1This is standards.info, produced by makeinfo version 4.8 from 2.././etc/standards.texi. 3 4START-INFO-DIR-ENTRY 5* Standards: (standards). GNU coding standards. 6END-INFO-DIR-ENTRY 7 8 GNU Coding Standards Copyright (C) 1992, 1993, 1994, 1995, 1996, 91997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc. 10 11 Permission is granted to copy, distribute and/or modify this document 12under the terms of the GNU Free Documentation License, Version 1.1 or 13any later version published by the Free Software Foundation; with no 14Invariant Sections, with no Front-Cover Texts, and with no Back-Cover 15Texts. A copy of the license is included in the section entitled "GNU 16Free Documentation License". 17 18 19File: standards.info, Node: Top, Next: Preface, Prev: (dir), Up: (dir) 20 21Version 22******* 23 24Last updated February 14, 2002. 25 26* Menu: 27 28* Preface:: About the GNU Coding Standards 29* Legal Issues:: Keeping Free Software Free 30* Design Advice:: General Program Design 31* Program Behavior:: Program Behavior for All Programs 32* Writing C:: Making The Best Use of C 33* Documentation:: Documenting Programs 34* Managing Releases:: The Release Process 35* References:: References to Non-Free Software or Documentation 36* Copying This Manual:: How to Make Copies of This Manual 37* Index:: 38 39 40File: standards.info, Node: Preface, Next: Legal Issues, Prev: Top, Up: Top 41 421 About the GNU Coding Standards 43******************************** 44 45The GNU Coding Standards were written by Richard Stallman and other GNU 46Project volunteers. Their purpose is to make the GNU system clean, 47consistent, and easy to install. This document can also be read as a 48guide to writing portable, robust and reliable programs. It focuses on 49programs written in C, but many of the rules and principles are useful 50even if you write in another programming language. The rules often 51state reasons for writing in a certain way. 52 53 This release of the GNU Coding Standards was last updated February 5414, 2002. 55 56 If you did not obtain this file directly from the GNU project and 57recently, please check for a newer version. You can ftp the GNU Coding 58Standards from any GNU FTP host in the directory `/pub/gnu/standards/'. 59The GNU Coding Standards are available there in several different 60formats: `standards.text', `standards.info', and `standards.dvi', as 61well as the Texinfo "source" which is divided in two files: 62`standards.texi' and `make-stds.texi'. The GNU Coding Standards are 63also available on the GNU World Wide Web server: 64`http://www.gnu.org/prep/standards_toc.html'. 65 66 Corrections or suggestions for this document should be sent to 67<bug-standards@gnu.org>. If you make a suggestion, please include a 68suggested new wording for it; our time is limited. We prefer a context 69diff to the `standards.texi' or `make-stds.texi' files, but if you 70don't have those files, please mail your suggestion anyway. 71 72 These standards cover the minimum of what is important when writing a 73GNU package. Likely, the needs for additional standards will come up. 74Sometimes, you might suggest that such standards be added to this 75document. If you think your standards would be generally useful, please 76do suggest them. 77 78 You should also set standards for your package on many questions not 79addressed or not firmly specified here. The most important point is to 80be self-consistent--try to stick to the conventions you pick, and try 81to document them as much as possible. That way, your program will be 82more maintainable by others. 83 84 85File: standards.info, Node: Legal Issues, Next: Design Advice, Prev: Preface, Up: Top 86 872 Keeping Free Software Free 88**************************** 89 90This node discusses how you can make sure that GNU software avoids 91legal difficulties, and other related issues. 92 93* Menu: 94 95* Reading Non-Free Code:: Referring to Proprietary Programs 96* Contributions:: Accepting Contributions 97* Trademarks:: How We Deal with Trademark Issues 98 99 100File: standards.info, Node: Reading Non-Free Code, Next: Contributions, Up: Legal Issues 101 1022.1 Referring to Proprietary Programs 103===================================== 104 105Don't in any circumstances refer to Unix source code for or during your 106work on GNU! (Or to any other proprietary programs.) 107 108 If you have a vague recollection of the internals of a Unix program, 109this does not absolutely mean you can't write an imitation of it, but 110do try to organize the imitation internally along different lines, 111because this is likely to make the details of the Unix version 112irrelevant and dissimilar to your results. 113 114 For example, Unix utilities were generally optimized to minimize 115memory use; if you go for speed instead, your program will be very 116different. You could keep the entire input file in core and scan it 117there instead of using stdio. Use a smarter algorithm discovered more 118recently than the Unix program. Eliminate use of temporary files. Do 119it in one pass instead of two (we did this in the assembler). 120 121 Or, on the contrary, emphasize simplicity instead of speed. For some 122applications, the speed of today's computers makes simpler algorithms 123adequate. 124 125 Or go for generality. For example, Unix programs often have static 126tables or fixed-size strings, which make for arbitrary limits; use 127dynamic allocation instead. Make sure your program handles NULs and 128other funny characters in the input files. Add a programming language 129for extensibility and write part of the program in that language. 130 131 Or turn some parts of the program into independently usable 132libraries. Or use a simple garbage collector instead of tracking 133precisely when to free memory, or use a new GNU facility such as 134obstacks. 135 136 137File: standards.info, Node: Contributions, Next: Trademarks, Prev: Reading Non-Free Code, Up: Legal Issues 138 1392.2 Accepting Contributions 140=========================== 141 142If the program you are working on is copyrighted by the Free Software 143Foundation, then when someone else sends you a piece of code to add to 144the program, we need legal papers to use it--just as we asked you to 145sign papers initially. _Each_ person who makes a nontrivial 146contribution to a program must sign some sort of legal papers in order 147for us to have clear title to the program; the main author alone is not 148enough. 149 150 So, before adding in any contributions from other people, please tell 151us, so we can arrange to get the papers. Then wait until we tell you 152that we have received the signed papers, before you actually use the 153contribution. 154 155 This applies both before you release the program and afterward. If 156you receive diffs to fix a bug, and they make significant changes, we 157need legal papers for that change. 158 159 This also applies to comments and documentation files. For copyright 160law, comments and code are just text. Copyright applies to all kinds of 161text, so we need legal papers for all kinds. 162 163 We know it is frustrating to ask for legal papers; it's frustrating 164for us as well. But if you don't wait, you are going out on a limb--for 165example, what if the contributor's employer won't sign a disclaimer? 166You might have to take that code out again! 167 168 You don't need papers for changes of a few lines here or there, since 169they are not significant for copyright purposes. Also, you don't need 170papers if all you get from the suggestion is some ideas, not actual code 171which you use. For example, if someone send you one implementation, but 172you write a different implementation of the same idea, you don't need to 173get papers. 174 175 The very worst thing is if you forget to tell us about the other 176contributor. We could be very embarrassed in court some day as a 177result. 178 179 We have more detailed advice for maintainers of programs; if you have 180reached the stage of actually maintaining a program for GNU (whether 181released or not), please ask us for a copy. 182 183 184File: standards.info, Node: Trademarks, Prev: Contributions, Up: Legal Issues 185 1862.3 Trademarks 187============== 188 189Please do not include any trademark acknowledgements in GNU software 190packages or documentation. 191 192 Trademark acknowledgements are the statements that such-and-such is a 193trademark of so-and-so. The GNU Project has no objection to the basic 194idea of trademarks, but these acknowledgements feel like kowtowing, so 195we don't use them. There is no legal requirement for them. 196 197 What is legally required, as regards other people's trademarks, is to 198avoid using them in ways which a reader might read as naming or labeling 199our own programs or activities. For example, since "Objective C" is 200(or at least was) a trademark, we made sure to say that we provide a 201"compiler for the Objective C language" rather than an "Objective C 202compiler". The latter is meant to be short for the former, but it does 203not explicitly state the relationship, so it could be misinterpreted as 204using "Objective C" as a label for the compiler rather than for the 205language. 206 207 208File: standards.info, Node: Design Advice, Next: Program Behavior, Prev: Legal Issues, Up: Top 209 2103 General Program Design 211************************ 212 213This node discusses some of the issues you should take into account 214when designing your program. 215 216* Menu: 217 218* Source Language:: Which languges to use. 219* Compatibility:: Compatibility with other implementations 220* Using Extensions:: Using non-standard features 221* Standard C:: Using Standard C features 222* Conditional Compilation:: Compiling Code Only If A Conditional is True 223 224 225File: standards.info, Node: Source Language, Next: Compatibility, Up: Design Advice 226 2273.1 Which Languages to Use 228========================== 229 230When you want to use a language that gets compiled and runs at high 231speed, the best language to use is C. Using another language is like 232using a non-standard feature: it will cause trouble for users. Even if 233GCC supports the other language, users may find it inconvenient to have 234to install the compiler for that other language in order to build your 235program. For example, if you write your program in C++, people will 236have to install the GNU C++ compiler in order to compile your program. 237 238 C has one other advantage over C++ and other compiled languages: more 239people know C, so more people will find it easy to read and modify the 240program if it is written in C. 241 242 So in general it is much better to use C, rather than the comparable 243alternatives. 244 245 But there are two exceptions to that conclusion: 246 247 * It is no problem to use another language to write a tool 248 specifically intended for use with that language. That is because 249 the only people who want to build the tool will be those who have 250 installed the other language anyway. 251 252 * If an application is of interest only to a narrow part of the 253 community, then the question of which language it is written in 254 has less effect on other people, so you may as well please 255 yourself. 256 257 Many programs are designed to be extensible: they include an 258interpreter for a language that is higher level than C. Often much of 259the program is written in that language, too. The Emacs editor 260pioneered this technique. 261 262 The standard extensibility interpreter for GNU software is GUILE, 263which implements the language Scheme (an especially clean and simple 264dialect of Lisp). `http://www.gnu.org/software/guile/'. We don't 265reject programs written in other "scripting languages" such as Perl and 266Python, but using GUILE is very important for the overall consistency of 267the GNU system. 268 269 270File: standards.info, Node: Compatibility, Next: Using Extensions, Prev: Source Language, Up: Design Advice 271 2723.2 Compatibility with Other Implementations 273============================================ 274 275With occasional exceptions, utility programs and libraries for GNU 276should be upward compatible with those in Berkeley Unix, and upward 277compatible with Standard C if Standard C specifies their behavior, and 278upward compatible with POSIX if POSIX specifies their behavior. 279 280 When these standards conflict, it is useful to offer compatibility 281modes for each of them. 282 283 Standard C and POSIX prohibit many kinds of extensions. Feel free 284to make the extensions anyway, and include a `--ansi', `--posix', or 285`--compatible' option to turn them off. However, if the extension has 286a significant chance of breaking any real programs or scripts, then it 287is not really upward compatible. So you should try to redesign its 288interface to make it upward compatible. 289 290 Many GNU programs suppress extensions that conflict with POSIX if the 291environment variable `POSIXLY_CORRECT' is defined (even if it is 292defined with a null value). Please make your program recognize this 293variable if appropriate. 294 295 When a feature is used only by users (not by programs or command 296files), and it is done poorly in Unix, feel free to replace it 297completely with something totally different and better. (For example, 298`vi' is replaced with Emacs.) But it is nice to offer a compatible 299feature as well. (There is a free `vi' clone, so we offer it.) 300 301 Additional useful features are welcome regardless of whether there 302is any precedent for them. 303 304 305File: standards.info, Node: Using Extensions, Next: Standard C, Prev: Compatibility, Up: Design Advice 306 3073.3 Using Non-standard Features 308=============================== 309 310Many GNU facilities that already exist support a number of convenient 311extensions over the comparable Unix facilities. Whether to use these 312extensions in implementing your program is a difficult question. 313 314 On the one hand, using the extensions can make a cleaner program. 315On the other hand, people will not be able to build the program unless 316the other GNU tools are available. This might cause the program to 317work on fewer kinds of machines. 318 319 With some extensions, it might be easy to provide both alternatives. 320For example, you can define functions with a "keyword" `INLINE' and 321define that as a macro to expand into either `inline' or nothing, 322depending on the compiler. 323 324 In general, perhaps it is best not to use the extensions if you can 325straightforwardly do without them, but to use the extensions if they 326are a big improvement. 327 328 An exception to this rule are the large, established programs (such 329as Emacs) which run on a great variety of systems. Using GNU 330extensions in such programs would make many users unhappy, so we don't 331do that. 332 333 Another exception is for programs that are used as part of 334compilation: anything that must be compiled with other compilers in 335order to bootstrap the GNU compilation facilities. If these require 336the GNU compiler, then no one can compile them without having them 337installed already. That would be extremely troublesome in certain 338cases. 339 340 341File: standards.info, Node: Standard C, Next: Conditional Compilation, Prev: Using Extensions, Up: Design Advice 342 3433.4 Standard C and Pre-Standard C 344================================= 345 3461989 Standard C is widespread enough now that it is ok to use its 347features in new programs. There is one exception: do not ever use the 348"trigraph" feature of Standard C. 349 350 1999 Standard C is not widespread yet, so please do not require its 351features in programs. It is ok to use its features if they are present. 352 353 However, it is easy to support pre-standard compilers in most 354programs, so if you know how to do that, feel free. If a program you 355are maintaining has such support, you should try to keep it working. 356 357 To support pre-standard C, instead of writing function definitions in 358standard prototype form, 359 360 int 361 foo (int x, int y) 362 ... 363 364write the definition in pre-standard style like this, 365 366 int 367 foo (x, y) 368 int x, y; 369 ... 370 371and use a separate declaration to specify the argument prototype: 372 373 int foo (int, int); 374 375 You need such a declaration anyway, in a header file, to get the 376benefit of prototypes in all the files where the function is called. 377And once you have the declaration, you normally lose nothing by writing 378the function definition in the pre-standard style. 379 380 This technique does not work for integer types narrower than `int'. 381If you think of an argument as being of a type narrower than `int', 382declare it as `int' instead. 383 384 There are a few special cases where this technique is hard to use. 385For example, if a function argument needs to hold the system type 386`dev_t', you run into trouble, because `dev_t' is shorter than `int' on 387some machines; but you cannot use `int' instead, because `dev_t' is 388wider than `int' on some machines. There is no type you can safely use 389on all machines in a non-standard definition. The only way to support 390non-standard C and pass such an argument is to check the width of 391`dev_t' using Autoconf and choose the argument type accordingly. This 392may not be worth the trouble. 393 394 In order to support pre-standard compilers that do not recognize 395prototypes, you may want to use a preprocessor macro like this: 396 397 /* Declare the prototype for a general external function. */ 398 #if defined (__STDC__) || defined (WINDOWSNT) 399 #define P_(proto) proto 400 #else 401 #define P_(proto) () 402 #endif 403 404 405File: standards.info, Node: Conditional Compilation, Prev: Standard C, Up: Design Advice 406 4073.5 Conditional Compilation 408=========================== 409 410When supporting configuration options already known when building your 411program we prefer using `if (... )' over conditional compilation, as in 412the former case the compiler is able to perform more extensive checking 413of all possible code paths. 414 415 For example, please write 416 417 if (HAS_FOO) 418 ... 419 else 420 ... 421 422 instead of: 423 424 #ifdef HAS_FOO 425 ... 426 #else 427 ... 428 #endif 429 430 A modern compiler such as GCC will generate exactly the same code in 431both cases, and we have been using similar techniques with good success 432in several projects. 433 434 While this is not a silver bullet solving all portability problems, 435following this policy would have saved the GCC project alone many person 436hours if not days per year. 437 438 In the case of function-like macros like `REVERSIBLE_CC_MODE' in GCC 439which cannot be simply used in `if( ...)' statements, there is an easy 440workaround. Simply introduce another macro `HAS_REVERSIBLE_CC_MODE' as 441in the following example: 442 443 #ifdef REVERSIBLE_CC_MODE 444 #define HAS_REVERSIBLE_CC_MODE 1 445 #else 446 #define HAS_REVERSIBLE_CC_MODE 0 447 #endif 448 449 450File: standards.info, Node: Program Behavior, Next: Writing C, Prev: Design Advice, Up: Top 451 4524 Program Behavior for All Programs 453*********************************** 454 455This node describes conventions for writing robust software. It also 456describes general standards for error messages, the command line 457interface, and how libraries should behave. 458 459* Menu: 460 461* Semantics:: Writing robust programs 462* Libraries:: Library behavior 463* Errors:: Formatting error messages 464* User Interfaces:: Standards about interfaces generally 465* Graphical Interfaces:: Standards for graphical interfaces 466* Command-Line Interfaces:: Standards for command line interfaces 467* Option Table:: Table of long options 468* Memory Usage:: When and how to care about memory needs 469* File Usage:: Which files to use, and where 470 471 472File: standards.info, Node: Semantics, Next: Libraries, Up: Program Behavior 473 4744.1 Writing Robust Programs 475=========================== 476 477Avoid arbitrary limits on the length or number of _any_ data structure, 478including file names, lines, files, and symbols, by allocating all data 479structures dynamically. In most Unix utilities, "long lines are 480silently truncated". This is not acceptable in a GNU utility. 481 482 Utilities reading files should not drop NUL characters, or any other 483nonprinting characters _including those with codes above 0177_. The 484only sensible exceptions would be utilities specifically intended for 485interface to certain types of terminals or printers that can't handle 486those characters. Whenever possible, try to make programs work 487properly with sequences of bytes that represent multibyte characters, 488using encodings such as UTF-8 and others. 489 490 Check every system call for an error return, unless you know you 491wish to ignore errors. Include the system error text (from `perror' or 492equivalent) in _every_ error message resulting from a failing system 493call, as well as the name of the file if any and the name of the 494utility. Just "cannot open foo.c" or "stat failed" is not sufficient. 495 496 Check every call to `malloc' or `realloc' to see if it returned 497zero. Check `realloc' even if you are making the block smaller; in a 498system that rounds block sizes to a power of 2, `realloc' may get a 499different block if you ask for less space. 500 501 In Unix, `realloc' can destroy the storage block if it returns zero. 502GNU `realloc' does not have this bug: if it fails, the original block 503is unchanged. Feel free to assume the bug is fixed. If you wish to 504run your program on Unix, and wish to avoid lossage in this case, you 505can use the GNU `malloc'. 506 507 You must expect `free' to alter the contents of the block that was 508freed. Anything you want to fetch from the block, you must fetch before 509calling `free'. 510 511 If `malloc' fails in a noninteractive program, make that a fatal 512error. In an interactive program (one that reads commands from the 513user), it is better to abort the command and return to the command 514reader loop. This allows the user to kill other processes to free up 515virtual memory, and then try the command again. 516 517 Use `getopt_long' to decode arguments, unless the argument syntax 518makes this unreasonable. 519 520 When static storage is to be written in during program execution, use 521explicit C code to initialize it. Reserve C initialized declarations 522for data that will not be changed. 523 524 Try to avoid low-level interfaces to obscure Unix data structures 525(such as file directories, utmp, or the layout of kernel memory), since 526these are less likely to work compatibly. If you need to find all the 527files in a directory, use `readdir' or some other high-level interface. 528These are supported compatibly by GNU. 529 530 The preferred signal handling facilities are the BSD variant of 531`signal', and the POSIX `sigaction' function; the alternative USG 532`signal' interface is an inferior design. 533 534 Nowadays, using the POSIX signal functions may be the easiest way to 535make a program portable. If you use `signal', then on GNU/Linux 536systems running GNU libc version 1, you should include `bsd/signal.h' 537instead of `signal.h', so as to get BSD behavior. It is up to you 538whether to support systems where `signal' has only the USG behavior, or 539give up on them. 540 541 In error checks that detect "impossible" conditions, just abort. 542There is usually no point in printing any message. These checks 543indicate the existence of bugs. Whoever wants to fix the bugs will have 544to read the source code and run a debugger. So explain the problem with 545comments in the source. The relevant data will be in variables, which 546are easy to examine with the debugger, so there is no point moving them 547elsewhere. 548 549 Do not use a count of errors as the exit status for a program. 550_That does not work_, because exit status values are limited to 8 bits 551(0 through 255). A single run of the program might have 256 errors; if 552you try to return 256 as the exit status, the parent process will see 0 553as the status, and it will appear that the program succeeded. 554 555 If you make temporary files, check the `TMPDIR' environment 556variable; if that variable is defined, use the specified directory 557instead of `/tmp'. 558 559 In addition, be aware that there is a possible security problem when 560creating temporary files in world-writable directories. In C, you can 561avoid this problem by creating temporary files in this manner: 562 563 fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0600); 564 565or by using the `mkstemps' function from libiberty. 566 567 In bash, use `set -C' to avoid this problem. 568 569 570File: standards.info, Node: Libraries, Next: Errors, Prev: Semantics, Up: Program Behavior 571 5724.2 Library Behavior 573==================== 574 575Try to make library functions reentrant. If they need to do dynamic 576storage allocation, at least try to avoid any nonreentrancy aside from 577that of `malloc' itself. 578 579 Here are certain name conventions for libraries, to avoid name 580conflicts. 581 582 Choose a name prefix for the library, more than two characters long. 583All external function and variable names should start with this prefix. 584In addition, there should only be one of these in any given library 585member. This usually means putting each one in a separate source file. 586 587 An exception can be made when two external symbols are always used 588together, so that no reasonable program could use one without the 589other; then they can both go in the same file. 590 591 External symbols that are not documented entry points for the user 592should have names beginning with `_'. The `_' should be followed by 593the chosen name prefix for the library, to prevent collisions with 594other libraries. These can go in the same files with user entry points 595if you like. 596 597 Static functions and variables can be used as you like and need not 598fit any naming convention. 599 600 601File: standards.info, Node: Errors, Next: User Interfaces, Prev: Libraries, Up: Program Behavior 602 6034.3 Formatting Error Messages 604============================= 605 606Error messages from compilers should look like this: 607 608 SOURCE-FILE-NAME:LINENO: MESSAGE 609 610If you want to mention the column number, use this format: 611 612 SOURCE-FILE-NAME:LINENO:COLUMN: MESSAGE 613 614Line numbers should start from 1 at the beginning of the file, and 615column numbers should start from 1 at the beginning of the line. (Both 616of these conventions are chosen for compatibility.) Calculate column 617numbers assuming that space and all ASCII printing characters have 618equal width, and assuming tab stops every 8 columns. 619 620 Error messages from other noninteractive programs should look like 621this: 622 623 PROGRAM:SOURCE-FILE-NAME:LINENO: MESSAGE 624 625when there is an appropriate source file, or like this: 626 627 PROGRAM: MESSAGE 628 629when there is no relevant source file. 630 631 If you want to mention the column number, use this format: 632 633 PROGRAM:SOURCE-FILE-NAME:LINENO:COLUMN: MESSAGE 634 635 In an interactive program (one that is reading commands from a 636terminal), it is better not to include the program name in an error 637message. The place to indicate which program is running is in the 638prompt or with the screen layout. (When the same program runs with 639input from a source other than a terminal, it is not interactive and 640would do best to print error messages using the noninteractive style.) 641 642 The string MESSAGE should not begin with a capital letter when it 643follows a program name and/or file name. Also, it should not end with 644a period. 645 646 Error messages from interactive programs, and other messages such as 647usage messages, should start with a capital letter. But they should not 648end with a period. 649 650 651File: standards.info, Node: User Interfaces, Next: Graphical Interfaces, Prev: Errors, Up: Program Behavior 652 6534.4 Standards for Interfaces Generally 654====================================== 655 656Please don't make the behavior of a utility depend on the name used to 657invoke it. It is useful sometimes to make a link to a utility with a 658different name, and that should not change what it does. 659 660 Instead, use a run time option or a compilation switch or both to 661select among the alternate behaviors. 662 663 Likewise, please don't make the behavior of the program depend on the 664type of output device it is used with. Device independence is an 665important principle of the system's design; do not compromise it merely 666to save someone from typing an option now and then. (Variation in error 667message syntax when using a terminal is ok, because that is a side issue 668that people do not depend on.) 669 670 If you think one behavior is most useful when the output is to a 671terminal, and another is most useful when the output is a file or a 672pipe, then it is usually best to make the default behavior the one that 673is useful with output to a terminal, and have an option for the other 674behavior. 675 676 Compatibility requires certain programs to depend on the type of 677output device. It would be disastrous if `ls' or `sh' did not do so in 678the way all users expect. In some of these cases, we supplement the 679program with a preferred alternate version that does not depend on the 680output device type. For example, we provide a `dir' program much like 681`ls' except that its default output format is always multi-column 682format. 683 684 685File: standards.info, Node: Graphical Interfaces, Next: Command-Line Interfaces, Prev: User Interfaces, Up: Program Behavior 686 6874.5 Standards for Graphical Interfaces 688====================================== 689 690When you write a program that provides a graphical user interface, 691please make it work with X Windows and the GTK toolkit unless the 692functionality specifically requires some alternative (for example, 693"displaying jpeg images while in console mode"). 694 695 In addition, please provide a command-line interface to control the 696functionality. (In many cases, the graphical user interface can be a 697separate program which invokes the command-line program.) This is so 698that the same jobs can be done from scripts. 699 700 Please also consider providing a CORBA interface (for use from 701GNOME), a library interface (for use from C), and perhaps a 702keyboard-driven console interface (for use by users from console mode). 703Once you are doing the work to provide the functionality and the 704graphical interface, these won't be much extra work. 705 706 707File: standards.info, Node: Command-Line Interfaces, Next: Option Table, Prev: Graphical Interfaces, Up: Program Behavior 708 7094.6 Standards for Command Line Interfaces 710========================================= 711 712It is a good idea to follow the POSIX guidelines for the command-line 713options of a program. The easiest way to do this is to use `getopt' to 714parse them. Note that the GNU version of `getopt' will normally permit 715options anywhere among the arguments unless the special argument `--' 716is used. This is not what POSIX specifies; it is a GNU extension. 717 718 Please define long-named options that are equivalent to the 719single-letter Unix-style options. We hope to make GNU more user 720friendly this way. This is easy to do with the GNU function 721`getopt_long'. 722 723 One of the advantages of long-named options is that they can be 724consistent from program to program. For example, users should be able 725to expect the "verbose" option of any GNU program which has one, to be 726spelled precisely `--verbose'. To achieve this uniformity, look at the 727table of common long-option names when you choose the option names for 728your program (*note Option Table::). 729 730 It is usually a good idea for file names given as ordinary arguments 731to be input files only; any output files would be specified using 732options (preferably `-o' or `--output'). Even if you allow an output 733file name as an ordinary argument for compatibility, try to provide an 734option as another way to specify it. This will lead to more consistency 735among GNU utilities, and fewer idiosyncracies for users to remember. 736 737 All programs should support two standard options: `--version' and 738`--help'. 739 740`--version' 741 This option should direct the program to print information about 742 its name, version, origin and legal status, all on standard 743 output, and then exit successfully. Other options and arguments 744 should be ignored once this is seen, and the program should not 745 perform its normal function. 746 747 The first line is meant to be easy for a program to parse; the 748 version number proper starts after the last space. In addition, 749 it contains the canonical name for this program, in this format: 750 751 GNU Emacs 19.30 752 753 The program's name should be a constant string; _don't_ compute it 754 from `argv[0]'. The idea is to state the standard or canonical 755 name for the program, not its file name. There are other ways to 756 find out the precise file name where a command is found in `PATH'. 757 758 If the program is a subsidiary part of a larger package, mention 759 the package name in parentheses, like this: 760 761 emacsserver (GNU Emacs) 19.30 762 763 If the package has a version number which is different from this 764 program's version number, you can mention the package version 765 number just before the close-parenthesis. 766 767 If you *need* to mention the version numbers of libraries which 768 are distributed separately from the package which contains this 769 program, you can do so by printing an additional line of version 770 info for each library you want to mention. Use the same format 771 for these lines as for the first line. 772 773 Please do not mention all of the libraries that the program uses 774 "just for completeness"--that would produce a lot of unhelpful 775 clutter. Please mention library version numbers only if you find 776 in practice that they are very important to you in debugging. 777 778 The following line, after the version number line or lines, should 779 be a copyright notice. If more than one copyright notice is 780 called for, put each on a separate line. 781 782 Next should follow a brief statement that the program is free 783 software, and that users are free to copy and change it on certain 784 conditions. If the program is covered by the GNU GPL, say so 785 here. Also mention that there is no warranty, to the extent 786 permitted by law. 787 788 It is ok to finish the output with a list of the major authors of 789 the program, as a way of giving credit. 790 791 Here's an example of output that follows these rules: 792 793 GNU Emacs 19.34.5 794 Copyright (C) 1996 Free Software Foundation, Inc. 795 GNU Emacs comes with NO WARRANTY, 796 to the extent permitted by law. 797 You may redistribute copies of GNU Emacs 798 under the terms of the GNU General Public License. 799 For more information about these matters, 800 see the files named COPYING. 801 802 You should adapt this to your program, of course, filling in the 803 proper year, copyright holder, name of program, and the references 804 to distribution terms, and changing the rest of the wording as 805 necessary. 806 807 This copyright notice only needs to mention the most recent year in 808 which changes were made--there's no need to list the years for 809 previous versions' changes. You don't have to mention the name of 810 the program in these notices, if that is inconvenient, since it 811 appeared in the first line. 812 813 Translations of the above lines must preserve the validity of the 814 copyright notices (*note Internationalization::). If the 815 translation's character set supports it, the `(C)' should be 816 replaced with the copyright symbol, as follows: 817 818 (the official copyright symbol, which is the letter C in a circle); 819 820 Write the word "Copyright" exactly like that, in English. Do not 821 translate it into another language. International treaties 822 recognize the English word "Copyright"; translations into other 823 languages do not have legal significance. 824 825`--help' 826 This option should output brief documentation for how to invoke the 827 program, on standard output, then exit successfully. Other 828 options and arguments should be ignored once this is seen, and the 829 program should not perform its normal function. 830 831 Near the end of the `--help' option's output there should be a line 832 that says where to mail bug reports. It should have this format: 833 834 Report bugs to MAILING-ADDRESS. 835 836 837File: standards.info, Node: Option Table, Next: Memory Usage, Prev: Command-Line Interfaces, Up: Program Behavior 838 8394.7 Table of Long Options 840========================= 841 842Here is a table of long options used by GNU programs. It is surely 843incomplete, but we aim to list all the options that a new program might 844want to be compatible with. If you use names not already in the table, 845please send <bug-standards@gnu.org> a list of them, with their 846meanings, so we can update the table. 847 848`after-date' 849 `-N' in `tar'. 850 851`all' 852 `-a' in `du', `ls', `nm', `stty', `uname', and `unexpand'. 853 854`all-text' 855 `-a' in `diff'. 856 857`almost-all' 858 `-A' in `ls'. 859 860`append' 861 `-a' in `etags', `tee', `time'; `-r' in `tar'. 862 863`archive' 864 `-a' in `cp'. 865 866`archive-name' 867 `-n' in `shar'. 868 869`arglength' 870 `-l' in `m4'. 871 872`ascii' 873 `-a' in `diff'. 874 875`assign' 876 `-v' in `gawk'. 877 878`assume-new' 879 `-W' in Make. 880 881`assume-old' 882 `-o' in Make. 883 884`auto-check' 885 `-a' in `recode'. 886 887`auto-pager' 888 `-a' in `wdiff'. 889 890`auto-reference' 891 `-A' in `ptx'. 892 893`avoid-wraps' 894 `-n' in `wdiff'. 895 896`background' 897 For server programs, run in the background. 898 899`backward-search' 900 `-B' in `ctags'. 901 902`basename' 903 `-f' in `shar'. 904 905`batch' 906 Used in GDB. 907 908`baud' 909 Used in GDB. 910 911`before' 912 `-b' in `tac'. 913 914`binary' 915 `-b' in `cpio' and `diff'. 916 917`bits-per-code' 918 `-b' in `shar'. 919 920`block-size' 921 Used in `cpio' and `tar'. 922 923`blocks' 924 `-b' in `head' and `tail'. 925 926`break-file' 927 `-b' in `ptx'. 928 929`brief' 930 Used in various programs to make output shorter. 931 932`bytes' 933 `-c' in `head', `split', and `tail'. 934 935`c++' 936 `-C' in `etags'. 937 938`catenate' 939 `-A' in `tar'. 940 941`cd' 942 Used in various programs to specify the directory to use. 943 944`changes' 945 `-c' in `chgrp' and `chown'. 946 947`classify' 948 `-F' in `ls'. 949 950`colons' 951 `-c' in `recode'. 952 953`command' 954 `-c' in `su'; `-x' in GDB. 955 956`compare' 957 `-d' in `tar'. 958 959`compat' 960 Used in `gawk'. 961 962`compress' 963 `-Z' in `tar' and `shar'. 964 965`concatenate' 966 `-A' in `tar'. 967 968`confirmation' 969 `-w' in `tar'. 970 971`context' 972 Used in `diff'. 973 974`copyleft' 975 `-W copyleft' in `gawk'. 976 977`copyright' 978 `-C' in `ptx', `recode', and `wdiff'; `-W copyright' in `gawk'. 979 980`core' 981 Used in GDB. 982 983`count' 984 `-q' in `who'. 985 986`count-links' 987 `-l' in `du'. 988 989`create' 990 Used in `tar' and `cpio'. 991 992`cut-mark' 993 `-c' in `shar'. 994 995`cxref' 996 `-x' in `ctags'. 997 998`date' 999 `-d' in `touch'. 1000 1001`debug' 1002 `-d' in Make and `m4'; `-t' in Bison. 1003 1004`define' 1005 `-D' in `m4'. 1006 1007`defines' 1008 `-d' in Bison and `ctags'. 1009 1010`delete' 1011 `-D' in `tar'. 1012 1013`dereference' 1014 `-L' in `chgrp', `chown', `cpio', `du', `ls', and `tar'. 1015 1016`dereference-args' 1017 `-D' in `du'. 1018 1019`device' 1020 Specify an I/O device (special file name). 1021 1022`diacritics' 1023 `-d' in `recode'. 1024 1025`dictionary-order' 1026 `-d' in `look'. 1027 1028`diff' 1029 `-d' in `tar'. 1030 1031`digits' 1032 `-n' in `csplit'. 1033 1034`directory' 1035 Specify the directory to use, in various programs. In `ls', it 1036 means to show directories themselves rather than their contents. 1037 In `rm' and `ln', it means to not treat links to directories 1038 specially. 1039 1040`discard-all' 1041 `-x' in `strip'. 1042 1043`discard-locals' 1044 `-X' in `strip'. 1045 1046`dry-run' 1047 `-n' in Make. 1048 1049`ed' 1050 `-e' in `diff'. 1051 1052`elide-empty-files' 1053 `-z' in `csplit'. 1054 1055`end-delete' 1056 `-x' in `wdiff'. 1057 1058`end-insert' 1059 `-z' in `wdiff'. 1060 1061`entire-new-file' 1062 `-N' in `diff'. 1063 1064`environment-overrides' 1065 `-e' in Make. 1066 1067`eof' 1068 `-e' in `xargs'. 1069 1070`epoch' 1071 Used in GDB. 1072 1073`error-limit' 1074 Used in `makeinfo'. 1075 1076`error-output' 1077 `-o' in `m4'. 1078 1079`escape' 1080 `-b' in `ls'. 1081 1082`exclude-from' 1083 `-X' in `tar'. 1084 1085`exec' 1086 Used in GDB. 1087 1088`exit' 1089 `-x' in `xargs'. 1090 1091`exit-0' 1092 `-e' in `unshar'. 1093 1094`expand-tabs' 1095 `-t' in `diff'. 1096 1097`expression' 1098 `-e' in `sed'. 1099 1100`extern-only' 1101 `-g' in `nm'. 1102 1103`extract' 1104 `-i' in `cpio'; `-x' in `tar'. 1105 1106`faces' 1107 `-f' in `finger'. 1108 1109`fast' 1110 `-f' in `su'. 1111 1112`fatal-warnings' 1113 `-E' in `m4'. 1114 1115`file' 1116 `-f' in `info', `gawk', Make, `mt', and `tar'; `-n' in `sed'; `-r' 1117 in `touch'. 1118 1119`field-separator' 1120 `-F' in `gawk'. 1121 1122`file-prefix' 1123 `-b' in Bison. 1124 1125`file-type' 1126 `-F' in `ls'. 1127 1128`files-from' 1129 `-T' in `tar'. 1130 1131`fill-column' 1132 Used in `makeinfo'. 1133 1134`flag-truncation' 1135 `-F' in `ptx'. 1136 1137`fixed-output-files' 1138 `-y' in Bison. 1139 1140`follow' 1141 `-f' in `tail'. 1142 1143`footnote-style' 1144 Used in `makeinfo'. 1145 1146`force' 1147 `-f' in `cp', `ln', `mv', and `rm'. 1148 1149`force-prefix' 1150 `-F' in `shar'. 1151 1152`foreground' 1153 For server programs, run in the foreground; in other words, don't 1154 do anything special to run the server in the background. 1155 1156`format' 1157 Used in `ls', `time', and `ptx'. 1158 1159`freeze-state' 1160 `-F' in `m4'. 1161 1162`fullname' 1163 Used in GDB. 1164 1165`gap-size' 1166 `-g' in `ptx'. 1167 1168`get' 1169 `-x' in `tar'. 1170 1171`graphic' 1172 `-i' in `ul'. 1173 1174`graphics' 1175 `-g' in `recode'. 1176 1177`group' 1178 `-g' in `install'. 1179 1180`gzip' 1181 `-z' in `tar' and `shar'. 1182 1183`hashsize' 1184 `-H' in `m4'. 1185 1186`header' 1187 `-h' in `objdump' and `recode' 1188 1189`heading' 1190 `-H' in `who'. 1191 1192`help' 1193 Used to ask for brief usage information. 1194 1195`here-delimiter' 1196 `-d' in `shar'. 1197 1198`hide-control-chars' 1199 `-q' in `ls'. 1200 1201`html' 1202 In `makeinfo', output HTML. 1203 1204`idle' 1205 `-u' in `who'. 1206 1207`ifdef' 1208 `-D' in `diff'. 1209 1210`ignore' 1211 `-I' in `ls'; `-x' in `recode'. 1212 1213`ignore-all-space' 1214 `-w' in `diff'. 1215 1216`ignore-backups' 1217 `-B' in `ls'. 1218 1219`ignore-blank-lines' 1220 `-B' in `diff'. 1221 1222`ignore-case' 1223 `-f' in `look' and `ptx'; `-i' in `diff' and `wdiff'. 1224 1225`ignore-errors' 1226 `-i' in Make. 1227 1228`ignore-file' 1229 `-i' in `ptx'. 1230 1231`ignore-indentation' 1232 `-I' in `etags'. 1233 1234`ignore-init-file' 1235 `-f' in Oleo. 1236 1237`ignore-interrupts' 1238 `-i' in `tee'. 1239 1240`ignore-matching-lines' 1241 `-I' in `diff'. 1242 1243`ignore-space-change' 1244 `-b' in `diff'. 1245 1246`ignore-zeros' 1247 `-i' in `tar'. 1248 1249`include' 1250 `-i' in `etags'; `-I' in `m4'. 1251 1252`include-dir' 1253 `-I' in Make. 1254 1255`incremental' 1256 `-G' in `tar'. 1257 1258`info' 1259 `-i', `-l', and `-m' in Finger. 1260 1261`init-file' 1262 In some programs, specify the name of the file to read as the 1263 user's init file. 1264 1265`initial' 1266 `-i' in `expand'. 1267 1268`initial-tab' 1269 `-T' in `diff'. 1270 1271`inode' 1272 `-i' in `ls'. 1273 1274`interactive' 1275 `-i' in `cp', `ln', `mv', `rm'; `-e' in `m4'; `-p' in `xargs'; 1276 `-w' in `tar'. 1277 1278`intermix-type' 1279 `-p' in `shar'. 1280 1281`iso-8601' 1282 Used in `date' 1283 1284`jobs' 1285 `-j' in Make. 1286 1287`just-print' 1288 `-n' in Make. 1289 1290`keep-going' 1291 `-k' in Make. 1292 1293`keep-files' 1294 `-k' in `csplit'. 1295 1296`kilobytes' 1297 `-k' in `du' and `ls'. 1298 1299`language' 1300 `-l' in `etags'. 1301 1302`less-mode' 1303 `-l' in `wdiff'. 1304 1305`level-for-gzip' 1306 `-g' in `shar'. 1307 1308`line-bytes' 1309 `-C' in `split'. 1310 1311`lines' 1312 Used in `split', `head', and `tail'. 1313 1314`link' 1315 `-l' in `cpio'. 1316 1317`lint' 1318`lint-old' 1319 Used in `gawk'. 1320 1321`list' 1322 `-t' in `cpio'; `-l' in `recode'. 1323 1324`list' 1325 `-t' in `tar'. 1326 1327`literal' 1328 `-N' in `ls'. 1329 1330`load-average' 1331 `-l' in Make. 1332 1333`login' 1334 Used in `su'. 1335 1336`machine' 1337 No listing of which programs already use this; someone should 1338 check to see if any actually do, and tell <gnu@gnu.org>. 1339 1340`macro-name' 1341 `-M' in `ptx'. 1342 1343`mail' 1344 `-m' in `hello' and `uname'. 1345 1346`make-directories' 1347 `-d' in `cpio'. 1348 1349`makefile' 1350 `-f' in Make. 1351 1352`mapped' 1353 Used in GDB. 1354 1355`max-args' 1356 `-n' in `xargs'. 1357 1358`max-chars' 1359 `-n' in `xargs'. 1360 1361`max-lines' 1362 `-l' in `xargs'. 1363 1364`max-load' 1365 `-l' in Make. 1366 1367`max-procs' 1368 `-P' in `xargs'. 1369 1370`mesg' 1371 `-T' in `who'. 1372 1373`message' 1374 `-T' in `who'. 1375 1376`minimal' 1377 `-d' in `diff'. 1378 1379`mixed-uuencode' 1380 `-M' in `shar'. 1381 1382`mode' 1383 `-m' in `install', `mkdir', and `mkfifo'. 1384 1385`modification-time' 1386 `-m' in `tar'. 1387 1388`multi-volume' 1389 `-M' in `tar'. 1390 1391`name-prefix' 1392 `-a' in Bison. 1393 1394`nesting-limit' 1395 `-L' in `m4'. 1396 1397`net-headers' 1398 `-a' in `shar'. 1399 1400`new-file' 1401 `-W' in Make. 1402 1403`no-builtin-rules' 1404 `-r' in Make. 1405 1406`no-character-count' 1407 `-w' in `shar'. 1408 1409`no-check-existing' 1410 `-x' in `shar'. 1411 1412`no-common' 1413 `-3' in `wdiff'. 1414 1415`no-create' 1416 `-c' in `touch'. 1417 1418`no-defines' 1419 `-D' in `etags'. 1420 1421`no-deleted' 1422 `-1' in `wdiff'. 1423 1424`no-dereference' 1425 `-d' in `cp'. 1426 1427`no-inserted' 1428 `-2' in `wdiff'. 1429 1430`no-keep-going' 1431 `-S' in Make. 1432 1433`no-lines' 1434 `-l' in Bison. 1435 1436`no-piping' 1437 `-P' in `shar'. 1438 1439`no-prof' 1440 `-e' in `gprof'. 1441 1442`no-regex' 1443 `-R' in `etags'. 1444 1445`no-sort' 1446 `-p' in `nm'. 1447 1448`no-split' 1449 Used in `makeinfo'. 1450 1451`no-static' 1452 `-a' in `gprof'. 1453 1454`no-time' 1455 `-E' in `gprof'. 1456 1457`no-timestamp' 1458 `-m' in `shar'. 1459 1460`no-validate' 1461 Used in `makeinfo'. 1462 1463`no-wait' 1464 Used in `emacsclient'. 1465 1466`no-warn' 1467 Used in various programs to inhibit warnings. 1468 1469`node' 1470 `-n' in `info'. 1471 1472`nodename' 1473 `-n' in `uname'. 1474 1475`nonmatching' 1476 `-f' in `cpio'. 1477 1478`nstuff' 1479 `-n' in `objdump'. 1480 1481`null' 1482 `-0' in `xargs'. 1483 1484`number' 1485 `-n' in `cat'. 1486 1487`number-nonblank' 1488 `-b' in `cat'. 1489 1490`numeric-sort' 1491 `-n' in `nm'. 1492 1493`numeric-uid-gid' 1494 `-n' in `cpio' and `ls'. 1495 1496`nx' 1497 Used in GDB. 1498 1499`old-archive' 1500 `-o' in `tar'. 1501 1502`old-file' 1503 `-o' in Make. 1504 1505`one-file-system' 1506 `-l' in `tar', `cp', and `du'. 1507 1508`only-file' 1509 `-o' in `ptx'. 1510 1511`only-prof' 1512 `-f' in `gprof'. 1513 1514`only-time' 1515 `-F' in `gprof'. 1516 1517`options' 1518 `-o' in `getopt', `fdlist', `fdmount', `fdmountd', and `fdumount'. 1519 1520`output' 1521 In various programs, specify the output file name. 1522 1523`output-prefix' 1524 `-o' in `shar'. 1525 1526`override' 1527 `-o' in `rm'. 1528 1529`overwrite' 1530 `-c' in `unshar'. 1531 1532`owner' 1533 `-o' in `install'. 1534 1535`paginate' 1536 `-l' in `diff'. 1537 1538`paragraph-indent' 1539 Used in `makeinfo'. 1540 1541`parents' 1542 `-p' in `mkdir' and `rmdir'. 1543 1544`pass-all' 1545 `-p' in `ul'. 1546 1547`pass-through' 1548 `-p' in `cpio'. 1549 1550`port' 1551 `-P' in `finger'. 1552 1553`portability' 1554 `-c' in `cpio' and `tar'. 1555 1556`posix' 1557 Used in `gawk'. 1558 1559`prefix-builtins' 1560 `-P' in `m4'. 1561 1562`prefix' 1563 `-f' in `csplit'. 1564 1565`preserve' 1566 Used in `tar' and `cp'. 1567 1568`preserve-environment' 1569 `-p' in `su'. 1570 1571`preserve-modification-time' 1572 `-m' in `cpio'. 1573 1574`preserve-order' 1575 `-s' in `tar'. 1576 1577`preserve-permissions' 1578 `-p' in `tar'. 1579 1580`print' 1581 `-l' in `diff'. 1582 1583`print-chars' 1584 `-L' in `cmp'. 1585 1586`print-data-base' 1587 `-p' in Make. 1588 1589`print-directory' 1590 `-w' in Make. 1591 1592`print-file-name' 1593 `-o' in `nm'. 1594 1595`print-symdefs' 1596 `-s' in `nm'. 1597 1598`printer' 1599 `-p' in `wdiff'. 1600 1601`prompt' 1602 `-p' in `ed'. 1603 1604`proxy' 1605 Specify an HTTP proxy. 1606 1607`query-user' 1608 `-X' in `shar'. 1609 1610`question' 1611 `-q' in Make. 1612 1613`quiet' 1614 Used in many programs to inhibit the usual output. *Note_* every 1615 program accepting `--quiet' should accept `--silent' as a synonym. 1616 1617`quiet-unshar' 1618 `-Q' in `shar' 1619 1620`quote-name' 1621 `-Q' in `ls'. 1622 1623`rcs' 1624 `-n' in `diff'. 1625 1626`re-interval' 1627 Used in `gawk'. 1628 1629`read-full-blocks' 1630 `-B' in `tar'. 1631 1632`readnow' 1633 Used in GDB. 1634 1635`recon' 1636 `-n' in Make. 1637 1638`record-number' 1639 `-R' in `tar'. 1640 1641`recursive' 1642 Used in `chgrp', `chown', `cp', `ls', `diff', and `rm'. 1643 1644`reference-limit' 1645 Used in `makeinfo'. 1646 1647`references' 1648 `-r' in `ptx'. 1649 1650`regex' 1651 `-r' in `tac' and `etags'. 1652 1653`release' 1654 `-r' in `uname'. 1655 1656`reload-state' 1657 `-R' in `m4'. 1658 1659`relocation' 1660 `-r' in `objdump'. 1661 1662`rename' 1663 `-r' in `cpio'. 1664 1665`replace' 1666 `-i' in `xargs'. 1667 1668`report-identical-files' 1669 `-s' in `diff'. 1670 1671`reset-access-time' 1672 `-a' in `cpio'. 1673 1674`reverse' 1675 `-r' in `ls' and `nm'. 1676 1677`reversed-ed' 1678 `-f' in `diff'. 1679 1680`right-side-defs' 1681 `-R' in `ptx'. 1682 1683`same-order' 1684 `-s' in `tar'. 1685 1686`same-permissions' 1687 `-p' in `tar'. 1688 1689`save' 1690 `-g' in `stty'. 1691 1692`se' 1693 Used in GDB. 1694 1695`sentence-regexp' 1696 `-S' in `ptx'. 1697 1698`separate-dirs' 1699 `-S' in `du'. 1700 1701`separator' 1702 `-s' in `tac'. 1703 1704`sequence' 1705 Used by `recode' to chose files or pipes for sequencing passes. 1706 1707`shell' 1708 `-s' in `su'. 1709 1710`show-all' 1711 `-A' in `cat'. 1712 1713`show-c-function' 1714 `-p' in `diff'. 1715 1716`show-ends' 1717 `-E' in `cat'. 1718 1719`show-function-line' 1720 `-F' in `diff'. 1721 1722`show-tabs' 1723 `-T' in `cat'. 1724 1725`silent' 1726 Used in many programs to inhibit the usual output. *Note_* every 1727 program accepting `--silent' should accept `--quiet' as a synonym. 1728 1729`size' 1730 `-s' in `ls'. 1731 1732`socket' 1733 Specify a file descriptor for a network server to use for its 1734 socket, instead of opening and binding a new socket. This 1735 provides a way to run, in a nonpriveledged process, a server that 1736 normally needs a reserved port number. 1737 1738`sort' 1739 Used in `ls'. 1740 1741`source' 1742 `-W source' in `gawk'. 1743 1744`sparse' 1745 `-S' in `tar'. 1746 1747`speed-large-files' 1748 `-H' in `diff'. 1749 1750`split-at' 1751 `-E' in `unshar'. 1752 1753`split-size-limit' 1754 `-L' in `shar'. 1755 1756`squeeze-blank' 1757 `-s' in `cat'. 1758 1759`start-delete' 1760 `-w' in `wdiff'. 1761 1762`start-insert' 1763 `-y' in `wdiff'. 1764 1765`starting-file' 1766 Used in `tar' and `diff' to specify which file within a directory 1767 to start processing with. 1768 1769`statistics' 1770 `-s' in `wdiff'. 1771 1772`stdin-file-list' 1773 `-S' in `shar'. 1774 1775`stop' 1776 `-S' in Make. 1777 1778`strict' 1779 `-s' in `recode'. 1780 1781`strip' 1782 `-s' in `install'. 1783 1784`strip-all' 1785 `-s' in `strip'. 1786 1787`strip-debug' 1788 `-S' in `strip'. 1789 1790`submitter' 1791 `-s' in `shar'. 1792 1793`suffix' 1794 `-S' in `cp', `ln', `mv'. 1795 1796`suffix-format' 1797 `-b' in `csplit'. 1798 1799`sum' 1800 `-s' in `gprof'. 1801 1802`summarize' 1803 `-s' in `du'. 1804 1805`symbolic' 1806 `-s' in `ln'. 1807 1808`symbols' 1809 Used in GDB and `objdump'. 1810 1811`synclines' 1812 `-s' in `m4'. 1813 1814`sysname' 1815 `-s' in `uname'. 1816 1817`tabs' 1818 `-t' in `expand' and `unexpand'. 1819 1820`tabsize' 1821 `-T' in `ls'. 1822 1823`terminal' 1824 `-T' in `tput' and `ul'. `-t' in `wdiff'. 1825 1826`text' 1827 `-a' in `diff'. 1828 1829`text-files' 1830 `-T' in `shar'. 1831 1832`time' 1833 Used in `ls' and `touch'. 1834 1835`timeout' 1836 Specify how long to wait before giving up on some operation. 1837 1838`to-stdout' 1839 `-O' in `tar'. 1840 1841`total' 1842 `-c' in `du'. 1843 1844`touch' 1845 `-t' in Make, `ranlib', and `recode'. 1846 1847`trace' 1848 `-t' in `m4'. 1849 1850`traditional' 1851 `-t' in `hello'; `-W traditional' in `gawk'; `-G' in `ed', `m4', 1852 and `ptx'. 1853 1854`tty' 1855 Used in GDB. 1856 1857`typedefs' 1858 `-t' in `ctags'. 1859 1860`typedefs-and-c++' 1861 `-T' in `ctags'. 1862 1863`typeset-mode' 1864 `-t' in `ptx'. 1865 1866`uncompress' 1867 `-z' in `tar'. 1868 1869`unconditional' 1870 `-u' in `cpio'. 1871 1872`undefine' 1873 `-U' in `m4'. 1874 1875`undefined-only' 1876 `-u' in `nm'. 1877 1878`update' 1879 `-u' in `cp', `ctags', `mv', `tar'. 1880 1881`usage' 1882 Used in `gawk'; same as `--help'. 1883 1884`uuencode' 1885 `-B' in `shar'. 1886 1887`vanilla-operation' 1888 `-V' in `shar'. 1889 1890`verbose' 1891 Print more information about progress. Many programs support this. 1892 1893`verify' 1894 `-W' in `tar'. 1895 1896`version' 1897 Print the version number. 1898 1899`version-control' 1900 `-V' in `cp', `ln', `mv'. 1901 1902`vgrind' 1903 `-v' in `ctags'. 1904 1905`volume' 1906 `-V' in `tar'. 1907 1908`what-if' 1909 `-W' in Make. 1910 1911`whole-size-limit' 1912 `-l' in `shar'. 1913 1914`width' 1915 `-w' in `ls' and `ptx'. 1916 1917`word-regexp' 1918 `-W' in `ptx'. 1919 1920`writable' 1921 `-T' in `who'. 1922 1923`zeros' 1924 `-z' in `gprof'. 1925 1926 1927File: standards.info, Node: Memory Usage, Next: File Usage, Prev: Option Table, Up: Program Behavior 1928 19294.8 Memory Usage 1930================ 1931 1932If a program typically uses just a few meg of memory, don't bother 1933making any effort to reduce memory usage. For example, if it is 1934impractical for other reasons to operate on files more than a few meg 1935long, it is reasonable to read entire input files into core to operate 1936on them. 1937 1938 However, for programs such as `cat' or `tail', that can usefully 1939operate on very large files, it is important to avoid using a technique 1940that would artificially limit the size of files it can handle. If a 1941program works by lines and could be applied to arbitrary user-supplied 1942input files, it should keep only a line in memory, because this is not 1943very hard and users will want to be able to operate on input files that 1944are bigger than will fit in core all at once. 1945 1946 If your program creates complicated data structures, just make them 1947in core and give a fatal error if `malloc' returns zero. 1948 1949 1950File: standards.info, Node: File Usage, Prev: Memory Usage, Up: Program Behavior 1951 19524.9 File Usage 1953============== 1954 1955Programs should be prepared to operate when `/usr' and `/etc' are 1956read-only file systems. Thus, if the program manages log files, lock 1957files, backup files, score files, or any other files which are modified 1958for internal purposes, these files should not be stored in `/usr' or 1959`/etc'. 1960 1961 There are two exceptions. `/etc' is used to store system 1962configuration information; it is reasonable for a program to modify 1963files in `/etc' when its job is to update the system configuration. 1964Also, if the user explicitly asks to modify one file in a directory, it 1965is reasonable for the program to store other files in the same 1966directory. 1967 1968 1969File: standards.info, Node: Writing C, Next: Documentation, Prev: Program Behavior, Up: Top 1970 19715 Making The Best Use of C 1972************************** 1973 1974This node provides advice on how best to use the C language when 1975writing GNU software. 1976 1977* Menu: 1978 1979* Formatting:: Formatting Your Source Code 1980* Comments:: Commenting Your Work 1981* Syntactic Conventions:: Clean Use of C Constructs 1982* Names:: Naming Variables, Functions, and Files 1983* System Portability:: Portability between different operating systems 1984* CPU Portability:: Supporting the range of CPU types 1985* System Functions:: Portability and ``standard'' library functions 1986* Internationalization:: Techniques for internationalization 1987* Mmap:: How you can safely use `mmap'. 1988 1989 1990File: standards.info, Node: Formatting, Next: Comments, Up: Writing C 1991 19925.1 Formatting Your Source Code 1993=============================== 1994 1995It is important to put the open-brace that starts the body of a C 1996function in column zero, and avoid putting any other open-brace or 1997open-parenthesis or open-bracket in column zero. Several tools look 1998for open-braces in column zero to find the beginnings of C functions. 1999These tools will not work on code not formatted that way. 2000 2001 It is also important for function definitions to start the name of 2002the function in column zero. This helps people to search for function 2003definitions, and may also help certain tools recognize them. Thus, the 2004proper format is this: 2005 2006 static char * 2007 concat (s1, s2) /* Name starts in column zero here */ 2008 char *s1, *s2; 2009 { /* Open brace in column zero here */ 2010 ... 2011 } 2012 2013or, if you want to use Standard C syntax, format the definition like 2014this: 2015 2016 static char * 2017 concat (char *s1, char *s2) 2018 { 2019 ... 2020 } 2021 2022 In Standard C, if the arguments don't fit nicely on one line, split 2023it like this: 2024 2025 int 2026 lots_of_args (int an_integer, long a_long, short a_short, 2027 double a_double, float a_float) 2028 ... 2029 2030 The rest of this section gives our recommendations for other aspects 2031of C formatting style, which is also the default style of the `indent' 2032program in version 1.2 and newer. It corresponds to the options 2033 2034 -nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2 2035 -ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -psl -nsc -nsob 2036 2037 We don't think of these recommendations as requirements, because it 2038causes no problems for users if two different programs have different 2039formatting styles. 2040 2041 But whatever style you use, please use it consistently, since a 2042mixture of styles within one program tends to look ugly. If you are 2043contributing changes to an existing program, please follow the style of 2044that program. 2045 2046 For the body of the function, our recommended style looks like this: 2047 2048 if (x < foo (y, z)) 2049 haha = bar[4] + 5; 2050 else 2051 { 2052 while (z) 2053 { 2054 haha += foo (z, z); 2055 z--; 2056 } 2057 return ++x + bar (); 2058 } 2059 2060 We find it easier to read a program when it has spaces before the 2061open-parentheses and after the commas. Especially after the commas. 2062 2063 When you split an expression into multiple lines, split it before an 2064operator, not after one. Here is the right way: 2065 2066 if (foo_this_is_long && bar > win (x, y, z) 2067 && remaining_condition) 2068 2069 Try to avoid having two operators of different precedence at the same 2070level of indentation. For example, don't write this: 2071 2072 mode = (inmode[j] == VOIDmode 2073 || GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]) 2074 ? outmode[j] : inmode[j]); 2075 2076 Instead, use extra parentheses so that the indentation shows the 2077nesting: 2078 2079 mode = ((inmode[j] == VOIDmode 2080 || (GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]))) 2081 ? outmode[j] : inmode[j]); 2082 2083 Insert extra parentheses so that Emacs will indent the code properly. 2084For example, the following indentation looks nice if you do it by hand, 2085 2086 v = rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 2087 + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000; 2088 2089but Emacs would alter it. Adding a set of parentheses produces 2090something that looks equally nice, and which Emacs will preserve: 2091 2092 v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 2093 + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000); 2094 2095 Format do-while statements like this: 2096 2097 do 2098 { 2099 a = foo (a); 2100 } 2101 while (a > 0); 2102 2103 Please use formfeed characters (control-L) to divide the program into 2104pages at logical places (but not within a function). It does not matter 2105just how long the pages are, since they do not have to fit on a printed 2106page. The formfeeds should appear alone on lines by themselves. 2107 2108 2109File: standards.info, Node: Comments, Next: Syntactic Conventions, Prev: Formatting, Up: Writing C 2110 21115.2 Commenting Your Work 2112======================== 2113 2114Every program should start with a comment saying briefly what it is for. 2115Example: `fmt - filter for simple filling of text'. 2116 2117 Please write the comments in a GNU program in English, because 2118English is the one language that nearly all programmers in all 2119countries can read. If you do not write English well, please write 2120comments in English as well as you can, then ask other people to help 2121rewrite them. If you can't write comments in English, please find 2122someone to work with you and translate your comments into English. 2123 2124 Please put a comment on each function saying what the function does, 2125what sorts of arguments it gets, and what the possible values of 2126arguments mean and are used for. It is not necessary to duplicate in 2127words the meaning of the C argument declarations, if a C type is being 2128used in its customary fashion. If there is anything nonstandard about 2129its use (such as an argument of type `char *' which is really the 2130address of the second character of a string, not the first), or any 2131possible values that would not work the way one would expect (such as, 2132that strings containing newlines are not guaranteed to work), be sure 2133to say so. 2134 2135 Also explain the significance of the return value, if there is one. 2136 2137 Please put two spaces after the end of a sentence in your comments, 2138so that the Emacs sentence commands will work. Also, please write 2139complete sentences and capitalize the first word. If a lower-case 2140identifier comes at the beginning of a sentence, don't capitalize it! 2141Changing the spelling makes it a different identifier. If you don't 2142like starting a sentence with a lower case letter, write the sentence 2143differently (e.g., "The identifier lower-case is ..."). 2144 2145 The comment on a function is much clearer if you use the argument 2146names to speak about the argument values. The variable name itself 2147should be lower case, but write it in upper case when you are speaking 2148about the value rather than the variable itself. Thus, "the inode 2149number NODE_NUM" rather than "an inode". 2150 2151 There is usually no purpose in restating the name of the function in 2152the comment before it, because the reader can see that for himself. 2153There might be an exception when the comment is so long that the 2154function itself would be off the bottom of the screen. 2155 2156 There should be a comment on each static variable as well, like this: 2157 2158 /* Nonzero means truncate lines in the display; 2159 zero means continue them. */ 2160 int truncate_lines; 2161 2162 Every `#endif' should have a comment, except in the case of short 2163conditionals (just a few lines) that are not nested. The comment should 2164state the condition of the conditional that is ending, _including its 2165sense_. `#else' should have a comment describing the condition _and 2166sense_ of the code that follows. For example: 2167 2168 #ifdef foo 2169 ... 2170 #else /* not foo */ 2171 ... 2172 #endif /* not foo */ 2173 #ifdef foo 2174 ... 2175 #endif /* foo */ 2176 2177but, by contrast, write the comments this way for a `#ifndef': 2178 2179 #ifndef foo 2180 ... 2181 #else /* foo */ 2182 ... 2183 #endif /* foo */ 2184 #ifndef foo 2185 ... 2186 #endif /* not foo */ 2187 2188 2189File: standards.info, Node: Syntactic Conventions, Next: Names, Prev: Comments, Up: Writing C 2190 21915.3 Clean Use of C Constructs 2192============================= 2193 2194Please explicitly declare the types of all objects. For example, you 2195should explicitly declare all arguments to functions, and you should 2196declare functions to return `int' rather than omitting the `int'. 2197 2198 Some programmers like to use the GCC `-Wall' option, and change the 2199code whenever it issues a warning. If you want to do this, then do. 2200Other programmers prefer not to use `-Wall', because it gives warnings 2201for valid and legitimate code which they do not want to change. If you 2202want to do this, then do. The compiler should be your servant, not 2203your master. 2204 2205 Declarations of external functions and functions to appear later in 2206the source file should all go in one place near the beginning of the 2207file (somewhere before the first function definition in the file), or 2208else should go in a header file. Don't put `extern' declarations inside 2209functions. 2210 2211 It used to be common practice to use the same local variables (with 2212names like `tem') over and over for different values within one 2213function. Instead of doing this, it is better declare a separate local 2214variable for each distinct purpose, and give it a name which is 2215meaningful. This not only makes programs easier to understand, it also 2216facilitates optimization by good compilers. You can also move the 2217declaration of each local variable into the smallest scope that includes 2218all its uses. This makes the program even cleaner. 2219 2220 Don't use local variables or parameters that shadow global 2221identifiers. 2222 2223 Don't declare multiple variables in one declaration that spans lines. 2224Start a new declaration on each line, instead. For example, instead of 2225this: 2226 2227 int foo, 2228 bar; 2229 2230write either this: 2231 2232 int foo, bar; 2233 2234or this: 2235 2236 int foo; 2237 int bar; 2238 2239(If they are global variables, each should have a comment preceding it 2240anyway.) 2241 2242 When you have an `if'-`else' statement nested in another `if' 2243statement, always put braces around the `if'-`else'. Thus, never write 2244like this: 2245 2246 if (foo) 2247 if (bar) 2248 win (); 2249 else 2250 lose (); 2251 2252always like this: 2253 2254 if (foo) 2255 { 2256 if (bar) 2257 win (); 2258 else 2259 lose (); 2260 } 2261 2262 If you have an `if' statement nested inside of an `else' statement, 2263either write `else if' on one line, like this, 2264 2265 if (foo) 2266 ... 2267 else if (bar) 2268 ... 2269 2270with its `then'-part indented like the preceding `then'-part, or write 2271the nested `if' within braces like this: 2272 2273 if (foo) 2274 ... 2275 else 2276 { 2277 if (bar) 2278 ... 2279 } 2280 2281 Don't declare both a structure tag and variables or typedefs in the 2282same declaration. Instead, declare the structure tag separately and 2283then use it to declare the variables or typedefs. 2284 2285 Try to avoid assignments inside `if'-conditions. For example, don't 2286write this: 2287 2288 if ((foo = (char *) malloc (sizeof *foo)) == 0) 2289 fatal ("virtual memory exhausted"); 2290 2291instead, write this: 2292 2293 foo = (char *) malloc (sizeof *foo); 2294 if (foo == 0) 2295 fatal ("virtual memory exhausted"); 2296 2297 Don't make the program ugly to placate `lint'. Please don't insert 2298any casts to `void'. Zero without a cast is perfectly fine as a null 2299pointer constant, except when calling a varargs function. 2300 2301 2302File: standards.info, Node: Names, Next: System Portability, Prev: Syntactic Conventions, Up: Writing C 2303 23045.4 Naming Variables, Functions, and Files 2305========================================== 2306 2307The names of global variables and functions in a program serve as 2308comments of a sort. So don't choose terse names--instead, look for 2309names that give useful information about the meaning of the variable or 2310function. In a GNU program, names should be English, like other 2311comments. 2312 2313 Local variable names can be shorter, because they are used only 2314within one context, where (presumably) comments explain their purpose. 2315 2316 Try to limit your use of abbreviations in symbol names. It is ok to 2317make a few abbreviations, explain what they mean, and then use them 2318frequently, but don't use lots of obscure abbreviations. 2319 2320 Please use underscores to separate words in a name, so that the Emacs 2321word commands can be useful within them. Stick to lower case; reserve 2322upper case for macros and `enum' constants, and for name-prefixes that 2323follow a uniform convention. 2324 2325 For example, you should use names like `ignore_space_change_flag'; 2326don't use names like `iCantReadThis'. 2327 2328 Variables that indicate whether command-line options have been 2329specified should be named after the meaning of the option, not after 2330the option-letter. A comment should state both the exact meaning of 2331the option and its letter. For example, 2332 2333 /* Ignore changes in horizontal whitespace (-b). */ 2334 int ignore_space_change_flag; 2335 2336 When you want to define names with constant integer values, use 2337`enum' rather than `#define'. GDB knows about enumeration constants. 2338 2339 You might want to make sure that none of the file names would 2340conflict the files were loaded onto an MS-DOS file system which 2341shortens the names. You can use the program `doschk' to test for this. 2342 2343 Some GNU programs were designed to limit themselves to file names of 234414 characters or less, to avoid file name conflicts if they are read 2345into older System V systems. Please preserve this feature in the 2346existing GNU programs that have it, but there is no need to do this in 2347new GNU programs. `doschk' also reports file names longer than 14 2348characters. 2349 2350 2351File: standards.info, Node: System Portability, Next: CPU Portability, Prev: Names, Up: Writing C 2352 23535.5 Portability between System Types 2354==================================== 2355 2356In the Unix world, "portability" refers to porting to different Unix 2357versions. For a GNU program, this kind of portability is desirable, but 2358not paramount. 2359 2360 The primary purpose of GNU software is to run on top of the GNU 2361kernel, compiled with the GNU C compiler, on various types of CPU. So 2362the kinds of portability that are absolutely necessary are quite 2363limited. But it is important to support Linux-based GNU systems, since 2364they are the form of GNU that is popular. 2365 2366 Beyond that, it is good to support the other free operating systems 2367(*BSD), and it is nice to support other Unix-like systems if you want 2368to. Supporting a variety of Unix-like systems is desirable, although 2369not paramount. It is usually not too hard, so you may as well do it. 2370But you don't have to consider it an obligation, if it does turn out to 2371be hard. 2372 2373 The easiest way to achieve portability to most Unix-like systems is 2374to use Autoconf. It's unlikely that your program needs to know more 2375information about the host platform than Autoconf can provide, simply 2376because most of the programs that need such knowledge have already been 2377written. 2378 2379 Avoid using the format of semi-internal data bases (e.g., 2380directories) when there is a higher-level alternative (`readdir'). 2381 2382 As for systems that are not like Unix, such as MSDOS, Windows, the 2383Macintosh, VMS, and MVS, supporting them is often a lot of work. When 2384that is the case, it is better to spend your time adding features that 2385will be useful on GNU and GNU/Linux, rather than on supporting other 2386incompatible systems. 2387 2388 It is a good idea to define the "feature test macro" `_GNU_SOURCE' 2389when compiling your C files. When you compile on GNU or GNU/Linux, 2390this will enable the declarations of GNU library extension functions, 2391and that will usually give you a compiler error message if you define 2392the same function names in some other way in your program. (You don't 2393have to actually _use_ these functions, if you prefer to make the 2394program more portable to other systems.) 2395 2396 But whether or not you use these GNU extensions, you should avoid 2397using their names for any other meanings. Doing so would make it hard 2398to move your code into other GNU programs. 2399 2400 2401File: standards.info, Node: CPU Portability, Next: System Functions, Prev: System Portability, Up: Writing C 2402 24035.6 Portability between CPUs 2404============================ 2405 2406Even GNU systems will differ because of differences among CPU 2407types--for example, difference in byte ordering and alignment 2408requirements. It is absolutely essential to handle these differences. 2409However, don't make any effort to cater to the possibility that an 2410`int' will be less than 32 bits. We don't support 16-bit machines in 2411GNU. 2412 2413 Similarly, don't make any effort to cater to the possibility that 2414`long' will be smaller than predefined types like `size_t'. For 2415example, the following code is ok: 2416 2417 printf ("size = %lu\n", (unsigned long) sizeof array); 2418 printf ("diff = %ld\n", (long) (pointer2 - pointer1)); 2419 2420 1989 Standard C requires this to work, and we know of only one 2421counterexample: 64-bit programs on Microsoft Windows IA-64. We will 2422leave it to those who want to port GNU programs to that environment to 2423figure out how to do it. 2424 2425 Predefined file-size types like `off_t' are an exception: they are 2426longer than `long' on many platforms, so code like the above won't work 2427with them. One way to print an `off_t' value portably is to print its 2428digits yourself, one by one. 2429 2430 Don't assume that the address of an `int' object is also the address 2431of its least-significant byte. This is false on big-endian machines. 2432Thus, don't make the following mistake: 2433 2434 int c; 2435 ... 2436 while ((c = getchar()) != EOF) 2437 write(file_descriptor, &c, 1); 2438 2439 When calling functions, you need not worry about the difference 2440between pointers of various types, or between pointers and integers. 2441On most machines, there's no difference anyway. As for the few 2442machines where there is a difference, all of them support Standard C 2443prototypes, so you can use prototypes (perhaps conditionalized to be 2444active only in Standard C) to make the code work on those systems. 2445 2446 In certain cases, it is ok to pass integer and pointer arguments 2447indiscriminately to the same function, and use no prototype on any 2448system. For example, many GNU programs have error-reporting functions 2449that pass their arguments along to `printf' and friends: 2450 2451 error (s, a1, a2, a3) 2452 char *s; 2453 char *a1, *a2, *a3; 2454 { 2455 fprintf (stderr, "error: "); 2456 fprintf (stderr, s, a1, a2, a3); 2457 } 2458 2459In practice, this works on all machines, since a pointer is generally 2460the widest possible kind of argument; it is much simpler than any 2461"correct" alternative. Be sure _not_ to use a prototype for such 2462functions. 2463 2464 If you have decided to use Standard C, then you can instead define 2465`error' using `stdarg.h', and pass the arguments along to `vfprintf'. 2466 2467 Avoid casting pointers to integers if you can. Such casts greatly 2468reduce portability, and in most programs they are easy to avoid. In the 2469cases where casting pointers to integers is essential--such as, a Lisp 2470interpreter which stores type information as well as an address in one 2471word--you'll have to make explicit provisions to handle different word 2472sizes. You will also need to make provision for systems in which the 2473normal range of addresses you can get from `malloc' starts far away 2474from zero. 2475 2476 2477File: standards.info, Node: System Functions, Next: Internationalization, Prev: CPU Portability, Up: Writing C 2478 24795.7 Calling System Functions 2480============================ 2481 2482C implementations differ substantially. Standard C reduces but does 2483not eliminate the incompatibilities; meanwhile, many GNU packages still 2484support pre-standard compilers because this is not hard to do. This 2485chapter gives recommendations for how to use the more-or-less standard C 2486library functions to avoid unnecessary loss of portability. 2487 2488 * Don't use the return value of `sprintf'. It returns the number of 2489 characters written on some systems, but not on all systems. 2490 2491 * Be aware that `vfprintf' is not always available. 2492 2493 * `main' should be declared to return type `int'. It should 2494 terminate either by calling `exit' or by returning the integer 2495 status code; make sure it cannot ever return an undefined value. 2496 2497 * Don't declare system functions explicitly. 2498 2499 Almost any declaration for a system function is wrong on some 2500 system. To minimize conflicts, leave it to the system header 2501 files to declare system functions. If the headers don't declare a 2502 function, let it remain undeclared. 2503 2504 While it may seem unclean to use a function without declaring it, 2505 in practice this works fine for most system library functions on 2506 the systems where this really happens; thus, the disadvantage is 2507 only theoretical. By contrast, actual declarations have 2508 frequently caused actual conflicts. 2509 2510 * If you must declare a system function, don't specify the argument 2511 types. Use an old-style declaration, not a Standard C prototype. 2512 The more you specify about the function, the more likely a 2513 conflict. 2514 2515 * In particular, don't unconditionally declare `malloc' or `realloc'. 2516 2517 Most GNU programs use those functions just once, in functions 2518 conventionally named `xmalloc' and `xrealloc'. These functions 2519 call `malloc' and `realloc', respectively, and check the results. 2520 2521 Because `xmalloc' and `xrealloc' are defined in your program, you 2522 can declare them in other files without any risk of type conflict. 2523 2524 On most systems, `int' is the same length as a pointer; thus, the 2525 calls to `malloc' and `realloc' work fine. For the few 2526 exceptional systems (mostly 64-bit machines), you can use 2527 *conditionalized* declarations of `malloc' and `realloc'--or put 2528 these declarations in configuration files specific to those 2529 systems. 2530 2531 * The string functions require special treatment. Some Unix systems 2532 have a header file `string.h'; others have `strings.h'. Neither 2533 file name is portable. There are two things you can do: use 2534 Autoconf to figure out which file to include, or don't include 2535 either file. 2536 2537 * If you don't include either strings file, you can't get 2538 declarations for the string functions from the header file in the 2539 usual way. 2540 2541 That causes less of a problem than you might think. The newer 2542 standard string functions should be avoided anyway because many 2543 systems still don't support them. The string functions you can 2544 use are these: 2545 2546 strcpy strncpy strcat strncat 2547 strlen strcmp strncmp 2548 strchr strrchr 2549 2550 The copy and concatenate functions work fine without a declaration 2551 as long as you don't use their values. Using their values without 2552 a declaration fails on systems where the width of a pointer 2553 differs from the width of `int', and perhaps in other cases. It 2554 is trivial to avoid using their values, so do that. 2555 2556 The compare functions and `strlen' work fine without a declaration 2557 on most systems, possibly all the ones that GNU software runs on. 2558 You may find it necessary to declare them *conditionally* on a few 2559 systems. 2560 2561 The search functions must be declared to return `char *'. Luckily, 2562 there is no variation in the data type they return. But there is 2563 variation in their names. Some systems give these functions the 2564 names `index' and `rindex'; other systems use the names `strchr' 2565 and `strrchr'. Some systems support both pairs of names, but 2566 neither pair works on all systems. 2567 2568 You should pick a single pair of names and use it throughout your 2569 program. (Nowadays, it is better to choose `strchr' and `strrchr' 2570 for new programs, since those are the standard names.) Declare 2571 both of those names as functions returning `char *'. On systems 2572 which don't support those names, define them as macros in terms of 2573 the other pair. For example, here is what to put at the beginning 2574 of your file (or in a header) if you want to use the names 2575 `strchr' and `strrchr' throughout: 2576 2577 #ifndef HAVE_STRCHR 2578 #define strchr index 2579 #endif 2580 #ifndef HAVE_STRRCHR 2581 #define strrchr rindex 2582 #endif 2583 2584 char *strchr (); 2585 char *strrchr (); 2586 2587 Here we assume that `HAVE_STRCHR' and `HAVE_STRRCHR' are macros 2588defined in systems where the corresponding functions exist. One way to 2589get them properly defined is to use Autoconf. 2590 2591 2592File: standards.info, Node: Internationalization, Next: Mmap, Prev: System Functions, Up: Writing C 2593 25945.8 Internationalization 2595======================== 2596 2597GNU has a library called GNU gettext that makes it easy to translate the 2598messages in a program into various languages. You should use this 2599library in every program. Use English for the messages as they appear 2600in the program, and let gettext provide the way to translate them into 2601other languages. 2602 2603 Using GNU gettext involves putting a call to the `gettext' macro 2604around each string that might need translation--like this: 2605 2606 printf (gettext ("Processing file `%s'...")); 2607 2608This permits GNU gettext to replace the string `"Processing file 2609`%s'..."' with a translated version. 2610 2611 Once a program uses gettext, please make a point of writing calls to 2612`gettext' when you add new strings that call for translation. 2613 2614 Using GNU gettext in a package involves specifying a "text domain 2615name" for the package. The text domain name is used to separate the 2616translations for this package from the translations for other packages. 2617Normally, the text domain name should be the same as the name of the 2618package--for example, `fileutils' for the GNU file utilities. 2619 2620 To enable gettext to work well, avoid writing code that makes 2621assumptions about the structure of words or sentences. When you want 2622the precise text of a sentence to vary depending on the data, use two or 2623more alternative string constants each containing a complete sentences, 2624rather than inserting conditionalized words or phrases into a single 2625sentence framework. 2626 2627 Here is an example of what not to do: 2628 2629 printf ("%d file%s processed", nfiles, 2630 nfiles != 1 ? "s" : ""); 2631 2632The problem with that example is that it assumes that plurals are made 2633by adding `s'. If you apply gettext to the format string, like this, 2634 2635 printf (gettext ("%d file%s processed"), nfiles, 2636 nfiles != 1 ? "s" : ""); 2637 2638the message can use different words, but it will still be forced to use 2639`s' for the plural. Here is a better way: 2640 2641 printf ((nfiles != 1 ? "%d files processed" 2642 : "%d file processed"), 2643 nfiles); 2644 2645This way, you can apply gettext to each of the two strings 2646independently: 2647 2648 printf ((nfiles != 1 ? gettext ("%d files processed") 2649 : gettext ("%d file processed")), 2650 nfiles); 2651 2652This can be any method of forming the plural of the word for "file", and 2653also handles languages that require agreement in the word for 2654"processed". 2655 2656 A similar problem appears at the level of sentence structure with 2657this code: 2658 2659 printf ("# Implicit rule search has%s been done.\n", 2660 f->tried_implicit ? "" : " not"); 2661 2662Adding `gettext' calls to this code cannot give correct results for all 2663languages, because negation in some languages requires adding words at 2664more than one place in the sentence. By contrast, adding `gettext' 2665calls does the job straightfowardly if the code starts out like this: 2666 2667 printf (f->tried_implicit 2668 ? "# Implicit rule search has been done.\n", 2669 : "# Implicit rule search has not been done.\n"); 2670 2671 2672File: standards.info, Node: Mmap, Prev: Internationalization, Up: Writing C 2673 26745.9 Mmap 2675======== 2676 2677Don't assume that `mmap' either works on all files or fails for all 2678files. It may work on some files and fail on others. 2679 2680 The proper way to use `mmap' is to try it on the specific file for 2681which you want to use it--and if `mmap' doesn't work, fall back on 2682doing the job in another way using `read' and `write'. 2683 2684 The reason this precaution is needed is that the GNU kernel (the 2685HURD) provides a user-extensible file system, in which there can be many 2686different kinds of "ordinary files." Many of them support `mmap', but 2687some do not. It is important to make programs handle all these kinds 2688of files. 2689 2690 2691File: standards.info, Node: Documentation, Next: Managing Releases, Prev: Writing C, Up: Top 2692 26936 Documenting Programs 2694********************** 2695 2696A GNU program should ideally come with full free documentation, adequate 2697for both reference and tutorial purposes. If the package can be 2698programmed or extended, the documentation should cover programming or 2699extending it, as well as just using it. 2700 2701* Menu: 2702 2703* GNU Manuals:: Writing proper manuals. 2704* Doc Strings and Manuals:: Compiling doc strings doesn't make a manual. 2705* Manual Structure Details:: Specific structure conventions. 2706* License for Manuals:: Writing the distribution terms for a manual. 2707* Manual Credits:: Giving credit to documentation contributors. 2708* Printed Manuals:: Mentioning the printed manual. 2709* NEWS File:: NEWS files supplement manuals. 2710* Change Logs:: Recording Changes 2711* Man Pages:: Man pages are secondary. 2712* Reading other Manuals:: How far you can go in learning 2713 from other manuals. 2714 2715 2716File: standards.info, Node: GNU Manuals, Next: Doc Strings and Manuals, Up: Documentation 2717 27186.1 GNU Manuals 2719=============== 2720 2721The preferred document format for the GNU system is the Texinfo 2722formatting language. Every GNU package should (ideally) have 2723documentation in Texinfo both for reference and for learners. Texinfo 2724makes it possible to produce a good quality formatted book, using TeX, 2725and to generate an Info file. It is also possible to generate HTML 2726output from Texinfo source. See the Texinfo manual, either the 2727hardcopy, or the on-line version available through `info' or the Emacs 2728Info subsystem (`C-h i'). 2729 2730 Nowadays some other formats such as Docbook and Sgmltexi can be 2731converted automatically into Texinfo. It is ok to produce the Texinfo 2732documentation by conversion this way, as long as it gives good results. 2733 2734 Programmers often find it most natural to structure the documentation 2735following the structure of the implementation, which they know. But 2736this structure is not necessarily good for explaining how to use the 2737program; it may be irrelevant and confusing for a user. 2738 2739 At every level, from the sentences in a paragraph to the grouping of 2740topics into separate manuals, the right way to structure documentation 2741is according to the concepts and questions that a user will have in mind 2742when reading it. Sometimes this structure of ideas matches the 2743structure of the implementation of the software being documented--but 2744often they are different. Often the most important part of learning to 2745write good documentation is learning to notice when you are structuring 2746the documentation like the implementation, and think about better 2747alternatives. 2748 2749 For example, each program in the GNU system probably ought to be 2750documented in one manual; but this does not mean each program should 2751have its own manual. That would be following the structure of the 2752implementation, rather than the structure that helps the user 2753understand. 2754 2755 Instead, each manual should cover a coherent _topic_. For example, 2756instead of a manual for `diff' and a manual for `diff3', we have one 2757manual for "comparison of files" which covers both of those programs, 2758as well as `cmp'. By documenting these programs together, we can make 2759the whole subject clearer. 2760 2761 The manual which discusses a program should certainly document all of 2762the program's command-line options and all of its commands. It should 2763give examples of their use. But don't organize the manual as a list of 2764features. Instead, organize it logically, by subtopics. Address the 2765questions that a user will ask when thinking about the job that the 2766program does. 2767 2768 In general, a GNU manual should serve both as tutorial and reference. 2769It should be set up for convenient access to each topic through Info, 2770and for reading straight through (appendixes aside). A GNU manual 2771should give a good introduction to a beginner reading through from the 2772start, and should also provide all the details that hackers want. The 2773Bison manual is a good example of this--please take a look at it to see 2774what we mean. 2775 2776 That is not as hard as it first sounds. Arrange each chapter as a 2777logical breakdown of its topic, but order the sections, and write their 2778text, so that reading the chapter straight through makes sense. Do 2779likewise when structuring the book into chapters, and when structuring a 2780section into paragraphs. The watchword is, _at each point, address the 2781most fundamental and important issue raised by the preceding text._ 2782 2783 If necessary, add extra chapters at the beginning of the manual which 2784are purely tutorial and cover the basics of the subject. These provide 2785the framework for a beginner to understand the rest of the manual. The 2786Bison manual provides a good example of how to do this. 2787 2788 To serve as a reference, a manual should have an Index that list all 2789the functions, variables, options, and important concepts that are part 2790of the program. One combined Index should do for a short manual, but 2791sometimes for a complex package it is better to use multiple indices. 2792The Texinfo manual includes advice on preparing good index entries, see 2793*Note Making Index Entries: (texinfo)Index Entries, and see *Note 2794Defining the Entries of an Index: (texinfo)Indexing Commands. 2795 2796 Don't use Unix man pages as a model for how to write GNU 2797documentation; most of them are terse, badly structured, and give 2798inadequate explanation of the underlying concepts. (There are, of 2799course, some exceptions.) Also, Unix man pages use a particular format 2800which is different from what we use in GNU manuals. 2801 2802 Please include an email address in the manual for where to report 2803bugs _in the manual_. 2804 2805 Please do not use the term "pathname" that is used in Unix 2806documentation; use "file name" (two words) instead. We use the term 2807"path" only for search paths, which are lists of directory names. 2808 2809 Please do not use the term "illegal" to refer to erroneous input to a 2810computer program. Please use "invalid" for this, and reserve the term 2811"illegal" for activities punishable by law. 2812 2813 2814File: standards.info, Node: Doc Strings and Manuals, Next: Manual Structure Details, Prev: GNU Manuals, Up: Documentation 2815 28166.2 Doc Strings and Manuals 2817=========================== 2818 2819Some programming systems, such as Emacs, provide a documentation string 2820for each function, command or variable. You may be tempted to write a 2821reference manual by compiling the documentation strings and writing a 2822little additional text to go around them--but you must not do it. That 2823approach is a fundamental mistake. The text of well-written 2824documentation strings will be entirely wrong for a manual. 2825 2826 A documentation string needs to stand alone--when it appears on the 2827screen, there will be no other text to introduce or explain it. 2828Meanwhile, it can be rather informal in style. 2829 2830 The text describing a function or variable in a manual must not stand 2831alone; it appears in the context of a section or subsection. Other text 2832at the beginning of the section should explain some of the concepts, and 2833should often make some general points that apply to several functions or 2834variables. The previous descriptions of functions and variables in the 2835section will also have given information about the topic. A description 2836written to stand alone would repeat some of that information; this 2837redundance looks bad. Meanwhile, the informality that is acceptable in 2838a documentation string is totally unacceptable in a manual. 2839 2840 The only good way to use documentation strings in writing a good 2841manual is to use them as a source of information for writing good text. 2842 2843 2844File: standards.info, Node: Manual Structure Details, Next: License for Manuals, Prev: Doc Strings and Manuals, Up: Documentation 2845 28466.3 Manual Structure Details 2847============================ 2848 2849The title page of the manual should state the version of the programs or 2850packages documented in the manual. The Top node of the manual should 2851also contain this information. If the manual is changing more 2852frequently than or independent of the program, also state a version 2853number for the manual in both of these places. 2854 2855 Each program documented in the manual should have a node named 2856`PROGRAM Invocation' or `Invoking PROGRAM'. This node (together with 2857its subnodes, if any) should describe the program's command line 2858arguments and how to run it (the sort of information people would look 2859in a man page for). Start with an `@example' containing a template for 2860all the options and arguments that the program uses. 2861 2862 Alternatively, put a menu item in some menu whose item name fits one 2863of the above patterns. This identifies the node which that item points 2864to as the node for this purpose, regardless of the node's actual name. 2865 2866 The `--usage' feature of the Info reader looks for such a node or 2867menu item in order to find the relevant text, so it is essential for 2868every Texinfo file to have one. 2869 2870 If one manual describes several programs, it should have such a node 2871for each program described in the manual. 2872 2873 2874File: standards.info, Node: License for Manuals, Next: Manual Credits, Prev: Manual Structure Details, Up: Documentation 2875 28766.4 License for Manuals 2877======================= 2878 2879Please use the GNU Free Documentation License for all GNU manuals that 2880are more than a few pages long. Likewise for a collection of short 2881documents--you only need one copy of the GNU FDL for the whole 2882collection. For a single short document, you can use a very permissive 2883non-copyleft license, to avoid taking up space with a long license. 2884 2885 See `http://www.gnu.org/copyleft/fdl-howto.html' for more explanation 2886of how to employ the GFDL. 2887 2888 Note that it is not obligatory to include a copy of the GNU GPL or 2889GNU LGPL in a manual whose license is neither the GPL nor the LGPL. It 2890can be a good idea to include the program's license in a large manual; 2891in a short manual, whose size would be increased considerably by 2892including the program's license, it is probably better not to include 2893it. 2894 2895 2896File: standards.info, Node: Manual Credits, Next: Printed Manuals, Prev: License for Manuals, Up: Documentation 2897 28986.5 Manual Credits 2899================== 2900 2901Please credit the principal human writers of the manual as the authors, 2902on the title page of the manual. If a company sponsored the work, thank 2903the company in a suitable place in the manual, but do not cite the 2904company as an author. 2905 2906 2907File: standards.info, Node: Printed Manuals, Next: NEWS File, Prev: Manual Credits, Up: Documentation 2908 29096.6 Printed Manuals 2910=================== 2911 2912The FSF publishes some GNU manuals in printed form. To encourage sales 2913of these manuals, the on-line versions of the manual should mention at 2914the very start that the printed manual is available and should point at 2915information for getting it--for instance, with a link to the page 2916`http://www.gnu.org/order/order.html'. This should not be included in 2917the printed manual, though, because there it is redundant. 2918 2919 It is also useful to explain in the on-line forms of the manual how 2920the user can print out the manual from the sources. 2921 2922 2923File: standards.info, Node: NEWS File, Next: Change Logs, Prev: Printed Manuals, Up: Documentation 2924 29256.7 The NEWS File 2926================= 2927 2928In addition to its manual, the package should have a file named `NEWS' 2929which contains a list of user-visible changes worth mentioning. In 2930each new release, add items to the front of the file and identify the 2931version they pertain to. Don't discard old items; leave them in the 2932file after the newer items. This way, a user upgrading from any 2933previous version can see what is new. 2934 2935 If the `NEWS' file gets very long, move some of the older items into 2936a file named `ONEWS' and put a note at the end referring the user to 2937that file. 2938 2939 2940File: standards.info, Node: Change Logs, Next: Man Pages, Prev: NEWS File, Up: Documentation 2941 29426.8 Change Logs 2943=============== 2944 2945Keep a change log to describe all the changes made to program source 2946files. The purpose of this is so that people investigating bugs in the 2947future will know about the changes that might have introduced the bug. 2948Often a new bug can be found by looking at what was recently changed. 2949More importantly, change logs can help you eliminate conceptual 2950inconsistencies between different parts of a program, by giving you a 2951history of how the conflicting concepts arose and who they came from. 2952 2953* Menu: 2954 2955* Change Log Concepts:: 2956* Style of Change Logs:: 2957* Simple Changes:: 2958* Conditional Changes:: 2959* Indicating the Part Changed:: 2960 2961 2962File: standards.info, Node: Change Log Concepts, Next: Style of Change Logs, Up: Change Logs 2963 29646.8.1 Change Log Concepts 2965------------------------- 2966 2967You can think of the change log as a conceptual "undo list" which 2968explains how earlier versions were different from the current version. 2969People can see the current version; they don't need the change log to 2970tell them what is in it. What they want from a change log is a clear 2971explanation of how the earlier version differed. 2972 2973 The change log file is normally called `ChangeLog' and covers an 2974entire directory. Each directory can have its own change log, or a 2975directory can use the change log of its parent directory-it's up to you. 2976 2977 Another alternative is to record change log information with a 2978version control system such as RCS or CVS. This can be converted 2979automatically to a `ChangeLog' file using `rcs2log'; in Emacs, the 2980command `C-x v a' (`vc-update-change-log') does the job. 2981 2982 There's no need to describe the full purpose of the changes or how 2983they work together. If you think that a change calls for explanation, 2984you're probably right. Please do explain it--but please put the 2985explanation in comments in the code, where people will see it whenever 2986they see the code. For example, "New function" is enough for the 2987change log when you add a function, because there should be a comment 2988before the function definition to explain what it does. 2989 2990 However, sometimes it is useful to write one line to describe the 2991overall purpose of a batch of changes. 2992 2993 The easiest way to add an entry to `ChangeLog' is with the Emacs 2994command `M-x add-change-log-entry'. An entry should have an asterisk, 2995the name of the changed file, and then in parentheses the name of the 2996changed functions, variables or whatever, followed by a colon. Then 2997describe the changes you made to that function or variable. 2998 2999 3000File: standards.info, Node: Style of Change Logs, Next: Simple Changes, Prev: Change Log Concepts, Up: Change Logs 3001 30026.8.2 Style of Change Logs 3003-------------------------- 3004 3005Here are some simple examples of change log entries, starting with the 3006header line that says who made the change and when, followed by 3007descriptions of specific changes. (These examples are drawn from Emacs 3008and GCC.) 3009 3010 1998-08-17 Richard Stallman <rms@gnu.org> 3011 3012 * register.el (insert-register): Return nil. 3013 (jump-to-register): Likewise. 3014 3015 * sort.el (sort-subr): Return nil. 3016 3017 * tex-mode.el (tex-bibtex-file, tex-file, tex-region): 3018 Restart the tex shell if process is gone or stopped. 3019 (tex-shell-running): New function. 3020 3021 * expr.c (store_one_arg): Round size up for move_block_to_reg. 3022 (expand_call): Round up when emitting USE insns. 3023 * stmt.c (assign_parms): Round size up for move_block_from_reg. 3024 3025 It's important to name the changed function or variable in full. 3026Don't abbreviate function or variable names, and don't combine them. 3027Subsequent maintainers will often search for a function name to find all 3028the change log entries that pertain to it; if you abbreviate the name, 3029they won't find it when they search. 3030 3031 For example, some people are tempted to abbreviate groups of function 3032names by writing `* register.el ({insert,jump-to}-register)'; this is 3033not a good idea, since searching for `jump-to-register' or 3034`insert-register' would not find that entry. 3035 3036 Separate unrelated change log entries with blank lines. When two 3037entries represent parts of the same change, so that they work together, 3038then don't put blank lines between them. Then you can omit the file 3039name and the asterisk when successive entries are in the same file. 3040 3041 Break long lists of function names by closing continued lines with 3042`)', rather than `,', and opening the continuation with `(' as in this 3043example: 3044 3045 * keyboard.c (menu_bar_items, tool_bar_items) 3046 (Fexecute_extended_command): Deal with `keymap' property. 3047 3048 3049File: standards.info, Node: Simple Changes, Next: Conditional Changes, Prev: Style of Change Logs, Up: Change Logs 3050 30516.8.3 Simple Changes 3052-------------------- 3053 3054Certain simple kinds of changes don't need much detail in the change 3055log. 3056 3057 When you change the calling sequence of a function in a simple 3058fashion, and you change all the callers of the function to use the new 3059calling sequence, there is no need to make individual entries for all 3060the callers that you changed. Just write in the entry for the function 3061being called, "All callers changed"--like this: 3062 3063 * keyboard.c (Fcommand_execute): New arg SPECIAL. 3064 All callers changed. 3065 3066 When you change just comments or doc strings, it is enough to write 3067an entry for the file, without mentioning the functions. Just "Doc 3068fixes" is enough for the change log. 3069 3070 There's no need to make change log entries for documentation files. 3071This is because documentation is not susceptible to bugs that are hard 3072to fix. Documentation does not consist of parts that must interact in a 3073precisely engineered fashion. To correct an error, you need not know 3074the history of the erroneous passage; it is enough to compare what the 3075documentation says with the way the program actually works. 3076 3077 3078File: standards.info, Node: Conditional Changes, Next: Indicating the Part Changed, Prev: Simple Changes, Up: Change Logs 3079 30806.8.4 Conditional Changes 3081------------------------- 3082 3083C programs often contain compile-time `#if' conditionals. Many changes 3084are conditional; sometimes you add a new definition which is entirely 3085contained in a conditional. It is very useful to indicate in the 3086change log the conditions for which the change applies. 3087 3088 Our convention for indicating conditional changes is to use square 3089brackets around the name of the condition. 3090 3091 Here is a simple example, describing a change which is conditional 3092but does not have a function or entity name associated with it: 3093 3094 * xterm.c [SOLARIS2]: Include string.h. 3095 3096 Here is an entry describing a new definition which is entirely 3097conditional. This new definition for the macro `FRAME_WINDOW_P' is 3098used only when `HAVE_X_WINDOWS' is defined: 3099 3100 * frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined. 3101 3102 Here is an entry for a change within the function `init_display', 3103whose definition as a whole is unconditional, but the changes themselves 3104are contained in a `#ifdef HAVE_LIBNCURSES' conditional: 3105 3106 * dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent. 3107 3108 Here is an entry for a change that takes affect only when a certain 3109macro is _not_ defined: 3110 3111 (gethostname) [!HAVE_SOCKETS]: Replace with winsock version. 3112 3113 3114File: standards.info, Node: Indicating the Part Changed, Prev: Conditional Changes, Up: Change Logs 3115 31166.8.5 Indicating the Part Changed 3117--------------------------------- 3118 3119Indicate the part of a function which changed by using angle brackets 3120enclosing an indication of what the changed part does. Here is an entry 3121for a change in the part of the function `sh-while-getopts' that deals 3122with `sh' commands: 3123 3124 * progmodes/sh-script.el (sh-while-getopts) <sh>: Handle case that 3125 user-specified option string is empty. 3126 3127 3128File: standards.info, Node: Man Pages, Next: Reading other Manuals, Prev: Change Logs, Up: Documentation 3129 31306.9 Man Pages 3131============= 3132 3133In the GNU project, man pages are secondary. It is not necessary or 3134expected for every GNU program to have a man page, but some of them do. 3135It's your choice whether to include a man page in your program. 3136 3137 When you make this decision, consider that supporting a man page 3138requires continual effort each time the program is changed. The time 3139you spend on the man page is time taken away from more useful work. 3140 3141 For a simple program which changes little, updating the man page may 3142be a small job. Then there is little reason not to include a man page, 3143if you have one. 3144 3145 For a large program that changes a great deal, updating a man page 3146may be a substantial burden. If a user offers to donate a man page, 3147you may find this gift costly to accept. It may be better to refuse 3148the man page unless the same person agrees to take full responsibility 3149for maintaining it--so that you can wash your hands of it entirely. If 3150this volunteer later ceases to do the job, then don't feel obliged to 3151pick it up yourself; it may be better to withdraw the man page from the 3152distribution until someone else agrees to update it. 3153 3154 When a program changes only a little, you may feel that the 3155discrepancies are small enough that the man page remains useful without 3156updating. If so, put a prominent note near the beginning of the man 3157page explaining that you don't maintain it and that the Texinfo manual 3158is more authoritative. The note should say how to access the Texinfo 3159documentation. 3160 3161 3162File: standards.info, Node: Reading other Manuals, Prev: Man Pages, Up: Documentation 3163 31646.10 Reading other Manuals 3165========================== 3166 3167There may be non-free books or documentation files that describe the 3168program you are documenting. 3169 3170 It is ok to use these documents for reference, just as the author of 3171a new algebra textbook can read other books on algebra. A large portion 3172of any non-fiction book consists of facts, in this case facts about how 3173a certain program works, and these facts are necessarily the same for 3174everyone who writes about the subject. But be careful not to copy your 3175outline structure, wording, tables or examples from preexisting non-free 3176documentation. Copying from free documentation may be ok; please check 3177with the FSF about the individual case. 3178 3179 3180File: standards.info, Node: Managing Releases, Next: References, Prev: Documentation, Up: Top 3181 31827 The Release Process 3183********************* 3184 3185Making a release is more than just bundling up your source files in a 3186tar file and putting it up for FTP. You should set up your software so 3187that it can be configured to run on a variety of systems. Your Makefile 3188should conform to the GNU standards described below, and your directory 3189layout should also conform to the standards discussed below. Doing so 3190makes it easy to include your package into the larger framework of all 3191GNU software. 3192 3193* Menu: 3194 3195* Configuration:: How Configuration Should Work 3196* Makefile Conventions:: Makefile Conventions 3197* Releases:: Making Releases 3198 3199 3200File: standards.info, Node: Configuration, Next: Makefile Conventions, Up: Managing Releases 3201 32027.1 How Configuration Should Work 3203================================= 3204 3205Each GNU distribution should come with a shell script named 3206`configure'. This script is given arguments which describe the kind of 3207machine and system you want to compile the program for. 3208 3209 The `configure' script must record the configuration options so that 3210they affect compilation. 3211 3212 One way to do this is to make a link from a standard name such as 3213`config.h' to the proper configuration file for the chosen system. If 3214you use this technique, the distribution should _not_ contain a file 3215named `config.h'. This is so that people won't be able to build the 3216program without configuring it first. 3217 3218 Another thing that `configure' can do is to edit the Makefile. If 3219you do this, the distribution should _not_ contain a file named 3220`Makefile'. Instead, it should include a file `Makefile.in' which 3221contains the input used for editing. Once again, this is so that people 3222won't be able to build the program without configuring it first. 3223 3224 If `configure' does write the `Makefile', then `Makefile' should 3225have a target named `Makefile' which causes `configure' to be rerun, 3226setting up the same configuration that was set up last time. The files 3227that `configure' reads should be listed as dependencies of `Makefile'. 3228 3229 All the files which are output from the `configure' script should 3230have comments at the beginning explaining that they were generated 3231automatically using `configure'. This is so that users won't think of 3232trying to edit them by hand. 3233 3234 The `configure' script should write a file named `config.status' 3235which describes which configuration options were specified when the 3236program was last configured. This file should be a shell script which, 3237if run, will recreate the same configuration. 3238 3239 The `configure' script should accept an option of the form 3240`--srcdir=DIRNAME' to specify the directory where sources are found (if 3241it is not the current directory). This makes it possible to build the 3242program in a separate directory, so that the actual source directory is 3243not modified. 3244 3245 If the user does not specify `--srcdir', then `configure' should 3246check both `.' and `..' to see if it can find the sources. If it finds 3247the sources in one of these places, it should use them from there. 3248Otherwise, it should report that it cannot find the sources, and should 3249exit with nonzero status. 3250 3251 Usually the easy way to support `--srcdir' is by editing a 3252definition of `VPATH' into the Makefile. Some rules may need to refer 3253explicitly to the specified source directory. To make this possible, 3254`configure' can add to the Makefile a variable named `srcdir' whose 3255value is precisely the specified directory. 3256 3257 The `configure' script should also take an argument which specifies 3258the type of system to build the program for. This argument should look 3259like this: 3260 3261 CPU-COMPANY-SYSTEM 3262 3263 For example, a Sun 3 might be `m68k-sun-sunos4.1'. 3264 3265 The `configure' script needs to be able to decode all plausible 3266alternatives for how to describe a machine. Thus, `sun3-sunos4.1' 3267would be a valid alias. For many programs, `vax-dec-ultrix' would be 3268an alias for `vax-dec-bsd', simply because the differences between 3269Ultrix and BSD are rarely noticeable, but a few programs might need to 3270distinguish them. 3271 3272 There is a shell script called `config.sub' that you can use as a 3273subroutine to validate system types and canonicalize aliases. 3274 3275 Other options are permitted to specify in more detail the software 3276or hardware present on the machine, and include or exclude optional 3277parts of the package: 3278 3279`--enable-FEATURE[=PARAMETER]' 3280 Configure the package to build and install an optional user-level 3281 facility called FEATURE. This allows users to choose which 3282 optional features to include. Giving an optional PARAMETER of 3283 `no' should omit FEATURE, if it is built by default. 3284 3285 No `--enable' option should *ever* cause one feature to replace 3286 another. No `--enable' option should ever substitute one useful 3287 behavior for another useful behavior. The only proper use for 3288 `--enable' is for questions of whether to build part of the program 3289 or exclude it. 3290 3291`--with-PACKAGE' 3292 The package PACKAGE will be installed, so configure this package 3293 to work with PACKAGE. 3294 3295 Possible values of PACKAGE include `gnu-as' (or `gas'), `gnu-ld', 3296 `gnu-libc', `gdb', `x', and `x-toolkit'. 3297 3298 Do not use a `--with' option to specify the file name to use to 3299 find certain files. That is outside the scope of what `--with' 3300 options are for. 3301 3302 All `configure' scripts should accept all of these "detail" options, 3303whether or not they make any difference to the particular package at 3304hand. In particular, they should accept any option that starts with 3305`--with-' or `--enable-'. This is so users will be able to configure 3306an entire GNU source tree at once with a single set of options. 3307 3308 You will note that the categories `--with-' and `--enable-' are 3309narrow: they *do not* provide a place for any sort of option you might 3310think of. That is deliberate. We want to limit the possible 3311configuration options in GNU software. We do not want GNU programs to 3312have idiosyncratic configuration options. 3313 3314 Packages that perform part of the compilation process may support 3315cross-compilation. In such a case, the host and target machines for the 3316program may be different. 3317 3318 The `configure' script should normally treat the specified type of 3319system as both the host and the target, thus producing a program which 3320works for the same type of machine that it runs on. 3321 3322 To configure a cross-compiler, cross-assembler, or what have you, you 3323should specify a target different from the host, using the configure 3324option `--target=TARGETTYPE'. The syntax for TARGETTYPE is the same as 3325for the host type. So the command would look like this: 3326 3327 ./configure HOSTTYPE --target=TARGETTYPE 3328 3329 Programs for which cross-operation is not meaningful need not accept 3330the `--target' option, because configuring an entire operating system 3331for cross-operation is not a meaningful operation. 3332 3333 Bootstrapping a cross-compiler requires compiling it on a machine 3334other than the host it will run on. Compilation packages accept a 3335configuration option `--build=BUILDTYPE' for specifying the 3336configuration on which you will compile them, but the configure script 3337should normally guess the build machine type (using `config.guess'), so 3338this option is probably not necessary. The host and target types 3339normally default from the build type, so in bootstrapping a 3340cross-compiler you must specify them both explicitly. 3341 3342 Some programs have ways of configuring themselves automatically. If 3343your program is set up to do this, your `configure' script can simply 3344ignore most of its arguments. 3345 3346 3347File: standards.info, Node: Makefile Conventions, Next: Releases, Prev: Configuration, Up: Managing Releases 3348 33497.2 Makefile Conventions 3350======================== 3351 3352This node describes conventions for writing the Makefiles for GNU 3353programs. Using Automake will help you write a Makefile that follows 3354these conventions. 3355 3356* Menu: 3357 3358* Makefile Basics:: General Conventions for Makefiles 3359* Utilities in Makefiles:: Utilities in Makefiles 3360* Command Variables:: Variables for Specifying Commands 3361* Directory Variables:: Variables for Installation Directories 3362* Standard Targets:: Standard Targets for Users 3363* Install Command Categories:: Three categories of commands in the `install' 3364 rule: normal, pre-install and post-install. 3365 3366 3367File: standards.info, Node: Makefile Basics, Next: Utilities in Makefiles, Up: Makefile Conventions 3368 33697.2.1 General Conventions for Makefiles 3370--------------------------------------- 3371 3372Every Makefile should contain this line: 3373 3374 SHELL = /bin/sh 3375 3376to avoid trouble on systems where the `SHELL' variable might be 3377inherited from the environment. (This is never a problem with GNU 3378`make'.) 3379 3380 Different `make' programs have incompatible suffix lists and 3381implicit rules, and this sometimes creates confusion or misbehavior. So 3382it is a good idea to set the suffix list explicitly using only the 3383suffixes you need in the particular Makefile, like this: 3384 3385 .SUFFIXES: 3386 .SUFFIXES: .c .o 3387 3388The first line clears out the suffix list, the second introduces all 3389suffixes which may be subject to implicit rules in this Makefile. 3390 3391 Don't assume that `.' is in the path for command execution. When 3392you need to run programs that are a part of your package during the 3393make, please make sure that it uses `./' if the program is built as 3394part of the make or `$(srcdir)/' if the file is an unchanging part of 3395the source code. Without one of these prefixes, the current search 3396path is used. 3397 3398 The distinction between `./' (the "build directory") and 3399`$(srcdir)/' (the "source directory") is important because users can 3400build in a separate directory using the `--srcdir' option to 3401`configure'. A rule of the form: 3402 3403 foo.1 : foo.man sedscript 3404 sed -e sedscript foo.man > foo.1 3405 3406will fail when the build directory is not the source directory, because 3407`foo.man' and `sedscript' are in the source directory. 3408 3409 When using GNU `make', relying on `VPATH' to find the source file 3410will work in the case where there is a single dependency file, since 3411the `make' automatic variable `$<' will represent the source file 3412wherever it is. (Many versions of `make' set `$<' only in implicit 3413rules.) A Makefile target like 3414 3415 foo.o : bar.c 3416 $(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o 3417 3418should instead be written as 3419 3420 foo.o : bar.c 3421 $(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@ 3422 3423in order to allow `VPATH' to work correctly. When the target has 3424multiple dependencies, using an explicit `$(srcdir)' is the easiest way 3425to make the rule work well. For example, the target above for `foo.1' 3426is best written as: 3427 3428 foo.1 : foo.man sedscript 3429 sed -e $(srcdir)/sedscript $(srcdir)/foo.man > $@ 3430 3431 GNU distributions usually contain some files which are not source 3432files--for example, Info files, and the output from Autoconf, Automake, 3433Bison or Flex. Since these files normally appear in the source 3434directory, they should always appear in the source directory, not in the 3435build directory. So Makefile rules to update them should put the 3436updated files in the source directory. 3437 3438 However, if a file does not appear in the distribution, then the 3439Makefile should not put it in the source directory, because building a 3440program in ordinary circumstances should not modify the source directory 3441in any way. 3442 3443 Try to make the build and installation targets, at least (and all 3444their subtargets) work correctly with a parallel `make'. 3445 3446 3447File: standards.info, Node: Utilities in Makefiles, Next: Command Variables, Prev: Makefile Basics, Up: Makefile Conventions 3448 34497.2.2 Utilities in Makefiles 3450---------------------------- 3451 3452Write the Makefile commands (and any shell scripts, such as 3453`configure') to run in `sh', not in `csh'. Don't use any special 3454features of `ksh' or `bash'. 3455 3456 The `configure' script and the Makefile rules for building and 3457installation should not use any utilities directly except these: 3458 3459 cat cmp cp diff echo egrep expr false grep install-info 3460 ln ls mkdir mv pwd rm rmdir sed sleep sort tar test touch true 3461 3462 The compression program `gzip' can be used in the `dist' rule. 3463 3464 Stick to the generally supported options for these programs. For 3465example, don't use `mkdir -p', convenient as it may be, because most 3466systems don't support it. 3467 3468 It is a good idea to avoid creating symbolic links in makefiles, 3469since a few systems don't support them. 3470 3471 The Makefile rules for building and installation can also use 3472compilers and related programs, but should do so via `make' variables 3473so that the user can substitute alternatives. Here are some of the 3474programs we mean: 3475 3476 ar bison cc flex install ld ldconfig lex 3477 make makeinfo ranlib texi2dvi yacc 3478 3479 Use the following `make' variables to run those programs: 3480 3481 $(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LDCONFIG) $(LEX) 3482 $(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC) 3483 3484 When you use `ranlib' or `ldconfig', you should make sure nothing 3485bad happens if the system does not have the program in question. 3486Arrange to ignore an error from that command, and print a message before 3487the command to tell the user that failure of this command does not mean 3488a problem. (The Autoconf `AC_PROG_RANLIB' macro can help with this.) 3489 3490 If you use symbolic links, you should implement a fallback for 3491systems that don't have symbolic links. 3492 3493 Additional utilities that can be used via Make variables are: 3494 3495 chgrp chmod chown mknod 3496 3497 It is ok to use other utilities in Makefile portions (or scripts) 3498intended only for particular systems where you know those utilities 3499exist. 3500 3501 3502File: standards.info, Node: Command Variables, Next: Directory Variables, Prev: Utilities in Makefiles, Up: Makefile Conventions 3503 35047.2.3 Variables for Specifying Commands 3505--------------------------------------- 3506 3507Makefiles should provide variables for overriding certain commands, 3508options, and so on. 3509 3510 In particular, you should run most utility programs via variables. 3511Thus, if you use Bison, have a variable named `BISON' whose default 3512value is set with `BISON = bison', and refer to it with `$(BISON)' 3513whenever you need to use Bison. 3514 3515 File management utilities such as `ln', `rm', `mv', and so on, need 3516not be referred to through variables in this way, since users don't 3517need to replace them with other programs. 3518 3519 Each program-name variable should come with an options variable that 3520is used to supply options to the program. Append `FLAGS' to the 3521program-name variable name to get the options variable name--for 3522example, `BISONFLAGS'. (The names `CFLAGS' for the C compiler, 3523`YFLAGS' for yacc, and `LFLAGS' for lex, are exceptions to this rule, 3524but we keep them because they are standard.) Use `CPPFLAGS' in any 3525compilation command that runs the preprocessor, and use `LDFLAGS' in 3526any compilation command that does linking as well as in any direct use 3527of `ld'. 3528 3529 If there are C compiler options that _must_ be used for proper 3530compilation of certain files, do not include them in `CFLAGS'. Users 3531expect to be able to specify `CFLAGS' freely themselves. Instead, 3532arrange to pass the necessary options to the C compiler independently 3533of `CFLAGS', by writing them explicitly in the compilation commands or 3534by defining an implicit rule, like this: 3535 3536 CFLAGS = -g 3537 ALL_CFLAGS = -I. $(CFLAGS) 3538 .c.o: 3539 $(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $< 3540 3541 Do include the `-g' option in `CFLAGS', because that is not 3542_required_ for proper compilation. You can consider it a default that 3543is only recommended. If the package is set up so that it is compiled 3544with GCC by default, then you might as well include `-O' in the default 3545value of `CFLAGS' as well. 3546 3547 Put `CFLAGS' last in the compilation command, after other variables 3548containing compiler options, so the user can use `CFLAGS' to override 3549the others. 3550 3551 `CFLAGS' should be used in every invocation of the C compiler, both 3552those which do compilation and those which do linking. 3553 3554 Every Makefile should define the variable `INSTALL', which is the 3555basic command for installing a file into the system. 3556 3557 Every Makefile should also define the variables `INSTALL_PROGRAM' 3558and `INSTALL_DATA'. (The default for `INSTALL_PROGRAM' should be 3559`$(INSTALL)'; the default for `INSTALL_DATA' should be `${INSTALL} -m 3560644'.) Then it should use those variables as the commands for actual 3561installation, for executables and nonexecutables respectively. Use 3562these variables as follows: 3563 3564 $(INSTALL_PROGRAM) foo $(bindir)/foo 3565 $(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a 3566 3567 Optionally, you may prepend the value of `DESTDIR' to the target 3568filename. Doing this allows the installer to create a snapshot of the 3569installation to be copied onto the real target filesystem later. Do not 3570set the value of `DESTDIR' in your Makefile, and do not include it in 3571any installed files. With support for `DESTDIR', the above examples 3572become: 3573 3574 $(INSTALL_PROGRAM) foo $(DESTDIR)$(bindir)/foo 3575 $(INSTALL_DATA) libfoo.a $(DESTDIR)$(libdir)/libfoo.a 3576 3577Always use a file name, not a directory name, as the second argument of 3578the installation commands. Use a separate command for each file to be 3579installed. 3580 3581 3582File: standards.info, Node: Directory Variables, Next: Standard Targets, Prev: Command Variables, Up: Makefile Conventions 3583 35847.2.4 Variables for Installation Directories 3585-------------------------------------------- 3586 3587Installation directories should always be named by variables, so it is 3588easy to install in a nonstandard place. The standard names for these 3589variables are described below. They are based on a standard filesystem 3590layout; variants of it are used in SVR4, 4.4BSD, GNU/Linux, Ultrix v4, 3591and other modern operating systems. 3592 3593 These two variables set the root for the installation. All the other 3594installation directories should be subdirectories of one of these two, 3595and nothing should be directly installed into these two directories. 3596 3597`prefix' 3598 A prefix used in constructing the default values of the variables 3599 listed below. The default value of `prefix' should be 3600 `/usr/local'. When building the complete GNU system, the prefix 3601 will be empty and `/usr' will be a symbolic link to `/'. (If you 3602 are using Autoconf, write it as `@prefix@'.) 3603 3604 Running `make install' with a different value of `prefix' from the 3605 one used to build the program should _not_ recompile the program. 3606 3607`exec_prefix' 3608 A prefix used in constructing the default values of some of the 3609 variables listed below. The default value of `exec_prefix' should 3610 be `$(prefix)'. (If you are using Autoconf, write it as 3611 `@exec_prefix@'.) 3612 3613 Generally, `$(exec_prefix)' is used for directories that contain 3614 machine-specific files (such as executables and subroutine 3615 libraries), while `$(prefix)' is used directly for other 3616 directories. 3617 3618 Running `make install' with a different value of `exec_prefix' 3619 from the one used to build the program should _not_ recompile the 3620 program. 3621 3622 Executable programs are installed in one of the following 3623directories. 3624 3625`bindir' 3626 The directory for installing executable programs that users can 3627 run. This should normally be `/usr/local/bin', but write it as 3628 `$(exec_prefix)/bin'. (If you are using Autoconf, write it as 3629 `@bindir@'.) 3630 3631`sbindir' 3632 The directory for installing executable programs that can be run 3633 from the shell, but are only generally useful to system 3634 administrators. This should normally be `/usr/local/sbin', but 3635 write it as `$(exec_prefix)/sbin'. (If you are using Autoconf, 3636 write it as `@sbindir@'.) 3637 3638`libexecdir' 3639 The directory for installing executable programs to be run by other 3640 programs rather than by users. This directory should normally be 3641 `/usr/local/libexec', but write it as `$(exec_prefix)/libexec'. 3642 (If you are using Autoconf, write it as `@libexecdir@'.) 3643 3644 Data files used by the program during its execution are divided into 3645categories in two ways. 3646 3647 * Some files are normally modified by programs; others are never 3648 normally modified (though users may edit some of these). 3649 3650 * Some files are architecture-independent and can be shared by all 3651 machines at a site; some are architecture-dependent and can be 3652 shared only by machines of the same kind and operating system; 3653 others may never be shared between two machines. 3654 3655 This makes for six different possibilities. However, we want to 3656discourage the use of architecture-dependent files, aside from object 3657files and libraries. It is much cleaner to make other data files 3658architecture-independent, and it is generally not hard. 3659 3660 Therefore, here are the variables Makefiles should use to specify 3661directories: 3662 3663`datadir' 3664 The directory for installing read-only architecture independent 3665 data files. This should normally be `/usr/local/share', but write 3666 it as `$(prefix)/share'. (If you are using Autoconf, write it as 3667 `@datadir@'.) As a special exception, see `$(infodir)' and 3668 `$(includedir)' below. 3669 3670`sysconfdir' 3671 The directory for installing read-only data files that pertain to a 3672 single machine-that is to say, files for configuring a host. 3673 Mailer and network configuration files, `/etc/passwd', and so 3674 forth belong here. All the files in this directory should be 3675 ordinary ASCII text files. This directory should normally be 3676 `/usr/local/etc', but write it as `$(prefix)/etc'. (If you are 3677 using Autoconf, write it as `@sysconfdir@'.) 3678 3679 Do not install executables here in this directory (they probably 3680 belong in `$(libexecdir)' or `$(sbindir)'). Also do not install 3681 files that are modified in the normal course of their use (programs 3682 whose purpose is to change the configuration of the system 3683 excluded). Those probably belong in `$(localstatedir)'. 3684 3685`sharedstatedir' 3686 The directory for installing architecture-independent data files 3687 which the programs modify while they run. This should normally be 3688 `/usr/local/com', but write it as `$(prefix)/com'. (If you are 3689 using Autoconf, write it as `@sharedstatedir@'.) 3690 3691`localstatedir' 3692 The directory for installing data files which the programs modify 3693 while they run, and that pertain to one specific machine. Users 3694 should never need to modify files in this directory to configure 3695 the package's operation; put such configuration information in 3696 separate files that go in `$(datadir)' or `$(sysconfdir)'. 3697 `$(localstatedir)' should normally be `/usr/local/var', but write 3698 it as `$(prefix)/var'. (If you are using Autoconf, write it as 3699 `@localstatedir@'.) 3700 3701`libdir' 3702 The directory for object files and libraries of object code. Do 3703 not install executables here, they probably ought to go in 3704 `$(libexecdir)' instead. The value of `libdir' should normally be 3705 `/usr/local/lib', but write it as `$(exec_prefix)/lib'. (If you 3706 are using Autoconf, write it as `@libdir@'.) 3707 3708`infodir' 3709 The directory for installing the Info files for this package. By 3710 default, it should be `/usr/local/info', but it should be written 3711 as `$(prefix)/info'. (If you are using Autoconf, write it as 3712 `@infodir@'.) 3713 3714`lispdir' 3715 The directory for installing any Emacs Lisp files in this package. 3716 By default, it should be `/usr/local/share/emacs/site-lisp', but 3717 it should be written as `$(prefix)/share/emacs/site-lisp'. 3718 3719 If you are using Autoconf, write the default as `@lispdir@'. In 3720 order to make `@lispdir@' work, you need the following lines in 3721 your `configure.in' file: 3722 3723 lispdir='${datadir}/emacs/site-lisp' 3724 AC_SUBST(lispdir) 3725 3726`includedir' 3727 The directory for installing header files to be included by user 3728 programs with the C `#include' preprocessor directive. This 3729 should normally be `/usr/local/include', but write it as 3730 `$(prefix)/include'. (If you are using Autoconf, write it as 3731 `@includedir@'.) 3732 3733 Most compilers other than GCC do not look for header files in 3734 directory `/usr/local/include'. So installing the header files 3735 this way is only useful with GCC. Sometimes this is not a problem 3736 because some libraries are only really intended to work with GCC. 3737 But some libraries are intended to work with other compilers. 3738 They should install their header files in two places, one 3739 specified by `includedir' and one specified by `oldincludedir'. 3740 3741`oldincludedir' 3742 The directory for installing `#include' header files for use with 3743 compilers other than GCC. This should normally be `/usr/include'. 3744 (If you are using Autoconf, you can write it as `@oldincludedir@'.) 3745 3746 The Makefile commands should check whether the value of 3747 `oldincludedir' is empty. If it is, they should not try to use 3748 it; they should cancel the second installation of the header files. 3749 3750 A package should not replace an existing header in this directory 3751 unless the header came from the same package. Thus, if your Foo 3752 package provides a header file `foo.h', then it should install the 3753 header file in the `oldincludedir' directory if either (1) there 3754 is no `foo.h' there or (2) the `foo.h' that exists came from the 3755 Foo package. 3756 3757 To tell whether `foo.h' came from the Foo package, put a magic 3758 string in the file--part of a comment--and `grep' for that string. 3759 3760 Unix-style man pages are installed in one of the following: 3761 3762`mandir' 3763 The top-level directory for installing the man pages (if any) for 3764 this package. It will normally be `/usr/local/man', but you should 3765 write it as `$(prefix)/man'. (If you are using Autoconf, write it 3766 as `@mandir@'.) 3767 3768`man1dir' 3769 The directory for installing section 1 man pages. Write it as 3770 `$(mandir)/man1'. 3771 3772`man2dir' 3773 The directory for installing section 2 man pages. Write it as 3774 `$(mandir)/man2' 3775 3776`...' 3777 *Don't make the primary documentation for any GNU software be a 3778 man page. Write a manual in Texinfo instead. Man pages are just 3779 for the sake of people running GNU software on Unix, which is a 3780 secondary application only.* 3781 3782`manext' 3783 The file name extension for the installed man page. This should 3784 contain a period followed by the appropriate digit; it should 3785 normally be `.1'. 3786 3787`man1ext' 3788 The file name extension for installed section 1 man pages. 3789 3790`man2ext' 3791 The file name extension for installed section 2 man pages. 3792 3793`...' 3794 Use these names instead of `manext' if the package needs to 3795 install man pages in more than one section of the manual. 3796 3797 And finally, you should set the following variable: 3798 3799`srcdir' 3800 The directory for the sources being compiled. The value of this 3801 variable is normally inserted by the `configure' shell script. 3802 (If you are using Autconf, use `srcdir = @srcdir@'.) 3803 3804 For example: 3805 3806 # Common prefix for installation directories. 3807 # NOTE: This directory must exist when you start the install. 3808 prefix = /usr/local 3809 exec_prefix = $(prefix) 3810 # Where to put the executable for the command `gcc'. 3811 bindir = $(exec_prefix)/bin 3812 # Where to put the directories used by the compiler. 3813 libexecdir = $(exec_prefix)/libexec 3814 # Where to put the Info files. 3815 infodir = $(prefix)/info 3816 3817 If your program installs a large number of files into one of the 3818standard user-specified directories, it might be useful to group them 3819into a subdirectory particular to that program. If you do this, you 3820should write the `install' rule to create these subdirectories. 3821 3822 Do not expect the user to include the subdirectory name in the value 3823of any of the variables listed above. The idea of having a uniform set 3824of variable names for installation directories is to enable the user to 3825specify the exact same values for several different GNU packages. In 3826order for this to be useful, all the packages must be designed so that 3827they will work sensibly when the user does so. 3828 3829 3830File: standards.info, Node: Standard Targets, Next: Install Command Categories, Prev: Directory Variables, Up: Makefile Conventions 3831 38327.2.5 Standard Targets for Users 3833-------------------------------- 3834 3835All GNU programs should have the following targets in their Makefiles: 3836 3837`all' 3838 Compile the entire program. This should be the default target. 3839 This target need not rebuild any documentation files; Info files 3840 should normally be included in the distribution, and DVI files 3841 should be made only when explicitly asked for. 3842 3843 By default, the Make rules should compile and link with `-g', so 3844 that executable programs have debugging symbols. Users who don't 3845 mind being helpless can strip the executables later if they wish. 3846 3847`install' 3848 Compile the program and copy the executables, libraries, and so on 3849 to the file names where they should reside for actual use. If 3850 there is a simple test to verify that a program is properly 3851 installed, this target should run that test. 3852 3853 Do not strip executables when installing them. Devil-may-care 3854 users can use the `install-strip' target to do that. 3855 3856 If possible, write the `install' target rule so that it does not 3857 modify anything in the directory where the program was built, 3858 provided `make all' has just been done. This is convenient for 3859 building the program under one user name and installing it under 3860 another. 3861 3862 The commands should create all the directories in which files are 3863 to be installed, if they don't already exist. This includes the 3864 directories specified as the values of the variables `prefix' and 3865 `exec_prefix', as well as all subdirectories that are needed. One 3866 way to do this is by means of an `installdirs' target as described 3867 below. 3868 3869 Use `-' before any command for installing a man page, so that 3870 `make' will ignore any errors. This is in case there are systems 3871 that don't have the Unix man page documentation system installed. 3872 3873 The way to install Info files is to copy them into `$(infodir)' 3874 with `$(INSTALL_DATA)' (*note Command Variables::), and then run 3875 the `install-info' program if it is present. `install-info' is a 3876 program that edits the Info `dir' file to add or update the menu 3877 entry for the given Info file; it is part of the Texinfo package. 3878 Here is a sample rule to install an Info file: 3879 3880 $(DESTDIR)$(infodir)/foo.info: foo.info 3881 $(POST_INSTALL) 3882 # There may be a newer info file in . than in srcdir. 3883 -if test -f foo.info; then d=.; \ 3884 else d=$(srcdir); fi; \ 3885 $(INSTALL_DATA) $$d/foo.info $(DESTDIR)$@; \ 3886 # Run install-info only if it exists. 3887 # Use `if' instead of just prepending `-' to the 3888 # line so we notice real errors from install-info. 3889 # We use `$(SHELL) -c' because some shells do not 3890 # fail gracefully when there is an unknown command. 3891 if $(SHELL) -c 'install-info --version' \ 3892 >/dev/null 2>&1; then \ 3893 install-info --dir-file=$(DESTDIR)$(infodir)/dir \ 3894 $(DESTDIR)$(infodir)/foo.info; \ 3895 else true; fi 3896 3897 When writing the `install' target, you must classify all the 3898 commands into three categories: normal ones, "pre-installation" 3899 commands and "post-installation" commands. *Note Install Command 3900 Categories::. 3901 3902`uninstall' 3903 Delete all the installed files--the copies that the `install' 3904 target creates. 3905 3906 This rule should not modify the directories where compilation is 3907 done, only the directories where files are installed. 3908 3909 The uninstallation commands are divided into three categories, 3910 just like the installation commands. *Note Install Command 3911 Categories::. 3912 3913`install-strip' 3914 Like `install', but strip the executable files while installing 3915 them. In simple cases, this target can use the `install' target in 3916 a simple way: 3917 3918 install-strip: 3919 $(MAKE) INSTALL_PROGRAM='$(INSTALL_PROGRAM) -s' \ 3920 install 3921 3922 But if the package installs scripts as well as real executables, 3923 the `install-strip' target can't just refer to the `install' 3924 target; it has to strip the executables but not the scripts. 3925 3926 `install-strip' should not strip the executables in the build 3927 directory which are being copied for installation. It should only 3928 strip the copies that are installed. 3929 3930 Normally we do not recommend stripping an executable unless you 3931 are sure the program has no bugs. However, it can be reasonable 3932 to install a stripped executable for actual execution while saving 3933 the unstripped executable elsewhere in case there is a bug. 3934 3935`clean' 3936 Delete all files from the current directory that are normally 3937 created by building the program. Don't delete the files that 3938 record the configuration. Also preserve files that could be made 3939 by building, but normally aren't because the distribution comes 3940 with them. 3941 3942 Delete `.dvi' files here if they are not part of the distribution. 3943 3944`distclean' 3945 Delete all files from the current directory that are created by 3946 configuring or building the program. If you have unpacked the 3947 source and built the program without creating any other files, 3948 `make distclean' should leave only the files that were in the 3949 distribution. 3950 3951`mostlyclean' 3952 Like `clean', but may refrain from deleting a few files that people 3953 normally don't want to recompile. For example, the `mostlyclean' 3954 target for GCC does not delete `libgcc.a', because recompiling it 3955 is rarely necessary and takes a lot of time. 3956 3957`maintainer-clean' 3958 Delete almost everything from the current directory that can be 3959 reconstructed with this Makefile. This typically includes 3960 everything deleted by `distclean', plus more: C source files 3961 produced by Bison, tags tables, Info files, and so on. 3962 3963 The reason we say "almost everything" is that running the command 3964 `make maintainer-clean' should not delete `configure' even if 3965 `configure' can be remade using a rule in the Makefile. More 3966 generally, `make maintainer-clean' should not delete anything that 3967 needs to exist in order to run `configure' and then begin to build 3968 the program. This is the only exception; `maintainer-clean' should 3969 delete everything else that can be rebuilt. 3970 3971 The `maintainer-clean' target is intended to be used by a 3972 maintainer of the package, not by ordinary users. You may need 3973 special tools to reconstruct some of the files that `make 3974 maintainer-clean' deletes. Since these files are normally 3975 included in the distribution, we don't take care to make them easy 3976 to reconstruct. If you find you need to unpack the full 3977 distribution again, don't blame us. 3978 3979 To help make users aware of this, the commands for the special 3980 `maintainer-clean' target should start with these two: 3981 3982 @echo 'This command is intended for maintainers to use; it' 3983 @echo 'deletes files that may need special tools to rebuild.' 3984 3985`TAGS' 3986 Update a tags table for this program. 3987 3988`info' 3989 Generate any Info files needed. The best way to write the rules 3990 is as follows: 3991 3992 info: foo.info 3993 3994 foo.info: foo.texi chap1.texi chap2.texi 3995 $(MAKEINFO) $(srcdir)/foo.texi 3996 3997 You must define the variable `MAKEINFO' in the Makefile. It should 3998 run the `makeinfo' program, which is part of the Texinfo 3999 distribution. 4000 4001 Normally a GNU distribution comes with Info files, and that means 4002 the Info files are present in the source directory. Therefore, 4003 the Make rule for an info file should update it in the source 4004 directory. When users build the package, ordinarily Make will not 4005 update the Info files because they will already be up to date. 4006 4007`dvi' 4008 Generate DVI files for all Texinfo documentation. For example: 4009 4010 dvi: foo.dvi 4011 4012 foo.dvi: foo.texi chap1.texi chap2.texi 4013 $(TEXI2DVI) $(srcdir)/foo.texi 4014 4015 You must define the variable `TEXI2DVI' in the Makefile. It should 4016 run the program `texi2dvi', which is part of the Texinfo 4017 distribution.(1) Alternatively, write just the dependencies, and 4018 allow GNU `make' to provide the command. 4019 4020`dist' 4021 Create a distribution tar file for this program. The tar file 4022 should be set up so that the file names in the tar file start with 4023 a subdirectory name which is the name of the package it is a 4024 distribution for. This name can include the version number. 4025 4026 For example, the distribution tar file of GCC version 1.40 unpacks 4027 into a subdirectory named `gcc-1.40'. 4028 4029 The easiest way to do this is to create a subdirectory 4030 appropriately named, use `ln' or `cp' to install the proper files 4031 in it, and then `tar' that subdirectory. 4032 4033 Compress the tar file with `gzip'. For example, the actual 4034 distribution file for GCC version 1.40 is called `gcc-1.40.tar.gz'. 4035 4036 The `dist' target should explicitly depend on all non-source files 4037 that are in the distribution, to make sure they are up to date in 4038 the distribution. *Note Making Releases: Releases. 4039 4040`check' 4041 Perform self-tests (if any). The user must build the program 4042 before running the tests, but need not install the program; you 4043 should write the self-tests so that they work when the program is 4044 built but not installed. 4045 4046 The following targets are suggested as conventional names, for 4047programs in which they are useful. 4048 4049`installcheck' 4050 Perform installation tests (if any). The user must build and 4051 install the program before running the tests. You should not 4052 assume that `$(bindir)' is in the search path. 4053 4054`installdirs' 4055 It's useful to add a target named `installdirs' to create the 4056 directories where files are installed, and their parent 4057 directories. There is a script called `mkinstalldirs' which is 4058 convenient for this; you can find it in the Texinfo package. You 4059 can use a rule like this: 4060 4061 # Make sure all installation directories (e.g. $(bindir)) 4062 # actually exist by making them if necessary. 4063 installdirs: mkinstalldirs 4064 $(srcdir)/mkinstalldirs $(bindir) $(datadir) \ 4065 $(libdir) $(infodir) \ 4066 $(mandir) 4067 4068 or, if you wish to support `DESTDIR', 4069 4070 # Make sure all installation directories (e.g. $(bindir)) 4071 # actually exist by making them if necessary. 4072 installdirs: mkinstalldirs 4073 $(srcdir)/mkinstalldirs \ 4074 $(DESTDIR)$(bindir) $(DESTDIR)$(datadir) \ 4075 $(DESTDIR)$(libdir) $(DESTDIR)$(infodir) \ 4076 $(DESTDIR)$(mandir) 4077 4078 This rule should not modify the directories where compilation is 4079 done. It should do nothing but create installation directories. 4080 4081 ---------- Footnotes ---------- 4082 4083 (1) `texi2dvi' uses TeX to do the real work of formatting. TeX is 4084not distributed with Texinfo. 4085 4086 4087File: standards.info, Node: Install Command Categories, Prev: Standard Targets, Up: Makefile Conventions 4088 40897.2.6 Install Command Categories 4090-------------------------------- 4091 4092When writing the `install' target, you must classify all the commands 4093into three categories: normal ones, "pre-installation" commands and 4094"post-installation" commands. 4095 4096 Normal commands move files into their proper places, and set their 4097modes. They may not alter any files except the ones that come entirely 4098from the package they belong to. 4099 4100 Pre-installation and post-installation commands may alter other 4101files; in particular, they can edit global configuration files or data 4102bases. 4103 4104 Pre-installation commands are typically executed before the normal 4105commands, and post-installation commands are typically run after the 4106normal commands. 4107 4108 The most common use for a post-installation command is to run 4109`install-info'. This cannot be done with a normal command, since it 4110alters a file (the Info directory) which does not come entirely and 4111solely from the package being installed. It is a post-installation 4112command because it needs to be done after the normal command which 4113installs the package's Info files. 4114 4115 Most programs don't need any pre-installation commands, but we have 4116the feature just in case it is needed. 4117 4118 To classify the commands in the `install' rule into these three 4119categories, insert "category lines" among them. A category line 4120specifies the category for the commands that follow. 4121 4122 A category line consists of a tab and a reference to a special Make 4123variable, plus an optional comment at the end. There are three 4124variables you can use, one for each category; the variable name 4125specifies the category. Category lines are no-ops in ordinary execution 4126because these three Make variables are normally undefined (and you 4127_should not_ define them in the makefile). 4128 4129 Here are the three possible category lines, each with a comment that 4130explains what it means: 4131 4132 $(PRE_INSTALL) # Pre-install commands follow. 4133 $(POST_INSTALL) # Post-install commands follow. 4134 $(NORMAL_INSTALL) # Normal commands follow. 4135 4136 If you don't use a category line at the beginning of the `install' 4137rule, all the commands are classified as normal until the first category 4138line. If you don't use any category lines, all the commands are 4139classified as normal. 4140 4141 These are the category lines for `uninstall': 4142 4143 $(PRE_UNINSTALL) # Pre-uninstall commands follow. 4144 $(POST_UNINSTALL) # Post-uninstall commands follow. 4145 $(NORMAL_UNINSTALL) # Normal commands follow. 4146 4147 Typically, a pre-uninstall command would be used for deleting entries 4148from the Info directory. 4149 4150 If the `install' or `uninstall' target has any dependencies which 4151act as subroutines of installation, then you should start _each_ 4152dependency's commands with a category line, and start the main target's 4153commands with a category line also. This way, you can ensure that each 4154command is placed in the right category regardless of which of the 4155dependencies actually run. 4156 4157 Pre-installation and post-installation commands should not run any 4158programs except for these: 4159 4160 [ basename bash cat chgrp chmod chown cmp cp dd diff echo 4161 egrep expand expr false fgrep find getopt grep gunzip gzip 4162 hostname install install-info kill ldconfig ln ls md5sum 4163 mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee 4164 test touch true uname xargs yes 4165 4166 The reason for distinguishing the commands in this way is for the 4167sake of making binary packages. Typically a binary package contains 4168all the executables and other files that need to be installed, and has 4169its own method of installing them--so it does not need to run the normal 4170installation commands. But installing the binary package does need to 4171execute the pre-installation and post-installation commands. 4172 4173 Programs to build binary packages work by extracting the 4174pre-installation and post-installation commands. Here is one way of 4175extracting the pre-installation commands: 4176 4177 make -n install -o all \ 4178 PRE_INSTALL=pre-install \ 4179 POST_INSTALL=post-install \ 4180 NORMAL_INSTALL=normal-install \ 4181 | gawk -f pre-install.awk 4182 4183where the file `pre-install.awk' could contain this: 4184 4185 $0 ~ /^\t[ \t]*(normal_install|post_install)[ \t]*$/ {on = 0} 4186 on {print $0} 4187 $0 ~ /^\t[ \t]*pre_install[ \t]*$/ {on = 1} 4188 4189 The resulting file of pre-installation commands is executed as a 4190shell script as part of installing the binary package. 4191 4192 4193File: standards.info, Node: Releases, Prev: Makefile Conventions, Up: Managing Releases 4194 41957.3 Making Releases 4196=================== 4197 4198Package the distribution of `Foo version 69.96' up in a gzipped tar 4199file with the name `foo-69.96.tar.gz'. It should unpack into a 4200subdirectory named `foo-69.96'. 4201 4202 Building and installing the program should never modify any of the 4203files contained in the distribution. This means that all the files 4204that form part of the program in any way must be classified into "source 4205files" and "non-source files". Source files are written by humans and 4206never changed automatically; non-source files are produced from source 4207files by programs under the control of the Makefile. 4208 4209 The distribution should contain a file named `README' which gives 4210the name of the package, and a general description of what it does. It 4211is also good to explain the purpose of each of the first-level 4212subdirectories in the package, if there are any. The `README' file 4213should either state the version number of the package, or refer to where 4214in the package it can be found. 4215 4216 The `README' file should refer to the file `INSTALL', which should 4217contain an explanation of the installation procedure. 4218 4219 The `README' file should also refer to the file which contains the 4220copying conditions. The GNU GPL, if used, should be in a file called 4221`COPYING'. If the GNU LGPL is used, it should be in a file called 4222`COPYING.LIB'. 4223 4224 Naturally, all the source files must be in the distribution. It is 4225okay to include non-source files in the distribution, provided they are 4226up-to-date and machine-independent, so that building the distribution 4227normally will never modify them. We commonly include non-source files 4228produced by Bison, `lex', TeX, and `makeinfo'; this helps avoid 4229unnecessary dependencies between our distributions, so that users can 4230install whichever packages they want to install. 4231 4232 Non-source files that might actually be modified by building and 4233installing the program should *never* be included in the distribution. 4234So if you do distribute non-source files, always make sure they are up 4235to date when you make a new distribution. 4236 4237 Make sure that the directory into which the distribution unpacks (as 4238well as any subdirectories) are all world-writable (octal mode 777). 4239This is so that old versions of `tar' which preserve the ownership and 4240permissions of the files from the tar archive will be able to extract 4241all the files even if the user is unprivileged. 4242 4243 Make sure that all the files in the distribution are world-readable. 4244 4245 Make sure that no file name in the distribution is more than 14 4246characters long. Likewise, no file created by building the program 4247should have a name longer than 14 characters. The reason for this is 4248that some systems adhere to a foolish interpretation of the POSIX 4249standard, and refuse to open a longer name, rather than truncating as 4250they did in the past. 4251 4252 Don't include any symbolic links in the distribution itself. If the 4253tar file contains symbolic links, then people cannot even unpack it on 4254systems that don't support symbolic links. Also, don't use multiple 4255names for one file in different directories, because certain file 4256systems cannot handle this and that prevents unpacking the distribution. 4257 4258 Try to make sure that all the file names will be unique on MS-DOS. A 4259name on MS-DOS consists of up to 8 characters, optionally followed by a 4260period and up to three characters. MS-DOS will truncate extra 4261characters both before and after the period. Thus, `foobarhacker.c' 4262and `foobarhacker.o' are not ambiguous; they are truncated to 4263`foobarha.c' and `foobarha.o', which are distinct. 4264 4265 Include in your distribution a copy of the `texinfo.tex' you used to 4266test print any `*.texinfo' or `*.texi' files. 4267 4268 Likewise, if your program uses small GNU software packages like 4269regex, getopt, obstack, or termcap, include them in the distribution 4270file. Leaving them out would make the distribution file a little 4271smaller at the expense of possible inconvenience to a user who doesn't 4272know what other files to get. 4273 4274 4275File: standards.info, Node: References, Next: Copying This Manual, Prev: Managing Releases, Up: Top 4276 42778 References to Non-Free Software and Documentation 4278*************************************************** 4279 4280A GNU program should not recommend use of any non-free program. We 4281can't stop some people from writing proprietary programs, or stop other 4282people from using them, but we can and should avoid helping to 4283advertise them to new potential customers. Proprietary software is a 4284social and ethical problem, and the point of GNU is to solve that 4285problem. 4286 4287 When a non-free program or system is well known, you can mention it 4288in passing--that is harmless, since users who might want to use it 4289probably already know about it. For instance, it is fine to explain 4290how to build your package on top of some non-free operating system, or 4291how to use it together with some widely used non-free program. 4292 4293 However, you should give only the necessary information to help those 4294who already use the non-free program to use your program with it--don't 4295give, or refer to, any further information about the proprietary 4296program, and don't imply that the proprietary program enhances your 4297program, or that its existence is in any way a good thing. The goal 4298should be that people already using the proprietary program will get 4299the advice they need about how to use your free program, while people 4300who don't already use the proprietary program will not see anything to 4301lead them to take an interest in it. 4302 4303 If a non-free program or system is obscure in your program's domain, 4304your program should not mention or support it at all, since doing so 4305would tend to popularize the non-free program more than it popularizes 4306your program. (You cannot hope to find many additional users among the 4307users of Foobar if the users of Foobar are few.) 4308 4309 A GNU package should not refer the user to any non-free documentation 4310for free software. Free documentation that can be included in free 4311operating systems is essential for completing the GNU system, so it is 4312a major focus of the GNU Project; to recommend use of documentation 4313that we are not allowed to use in GNU would undermine the efforts to 4314get documentation that we can include. So GNU packages should never 4315recommend non-free documentation. 4316 4317 4318File: standards.info, Node: Copying This Manual, Next: Index, Prev: References, Up: Top 4319 4320Appendix A Copying This Manual 4321****************************** 4322 4323* Menu: 4324 4325* GNU Free Documentation License:: License for copying this manual 4326 4327 4328File: standards.info, Node: GNU Free Documentation License, Up: Copying This Manual 4329 4330Appendix B GNU Free Documentation License 4331***************************************** 4332 4333 Version 1.1, March 2000 4334 4335 Copyright (C) 2000 Free Software Foundation, Inc. 4336 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 4337 4338 Everyone is permitted to copy and distribute verbatim copies 4339 of this license document, but changing it is not allowed. 4340 4341 4342 0. PREAMBLE 4343 4344 The purpose of this License is to make a manual, textbook, or other 4345 written document "free" in the sense of freedom: to assure everyone 4346 the effective freedom to copy and redistribute it, with or without 4347 modifying it, either commercially or noncommercially. Secondarily, 4348 this License preserves for the author and publisher a way to get 4349 credit for their work, while not being considered responsible for 4350 modifications made by others. 4351 4352 This License is a kind of "copyleft", which means that derivative 4353 works of the document must themselves be free in the same sense. 4354 It complements the GNU General Public License, which is a copyleft 4355 license designed for free software. 4356 4357 We have designed this License in order to use it for manuals for 4358 free software, because free software needs free documentation: a 4359 free program should come with manuals providing the same freedoms 4360 that the software does. But this License is not limited to 4361 software manuals; it can be used for any textual work, regardless 4362 of subject matter or whether it is published as a printed book. 4363 We recommend this License principally for works whose purpose is 4364 instruction or reference. 4365 4366 4367 1. APPLICABILITY AND DEFINITIONS 4368 4369 This License applies to any manual or other work that contains a 4370 notice placed by the copyright holder saying it can be distributed 4371 under the terms of this License. The "Document", below, refers to 4372 any such manual or work. Any member of the public is a licensee, 4373 and is addressed as "you." 4374 4375 A "Modified Version" of the Document means any work containing the 4376 Document or a portion of it, either copied verbatim, or with 4377 modifications and/or translated into another language. 4378 4379 A "Secondary Section" is a named appendix or a front-matter 4380 section of the Document that deals exclusively with the 4381 relationship of the publishers or authors of the Document to the 4382 Document's overall subject (or to related matters) and contains 4383 nothing that could fall directly within that overall subject. 4384 (For example, if the Document is in part a textbook of 4385 mathematics, a Secondary Section may not explain any mathematics.) 4386 The relationship could be a matter of historical connection with 4387 the subject or with related matters, or of legal, commercial, 4388 philosophical, ethical or political position regarding them. 4389 4390 The "Invariant Sections" are certain Secondary Sections whose 4391 titles are designated, as being those of Invariant Sections, in 4392 the notice that says that the Document is released under this 4393 License. 4394 4395 The "Cover Texts" are certain short passages of text that are 4396 listed, as Front-Cover Texts or Back-Cover Texts, in the notice 4397 that says that the Document is released under this License. 4398 4399 A "Transparent" copy of the Document means a machine-readable copy, 4400 represented in a format whose specification is available to the 4401 general public, whose contents can be viewed and edited directly 4402 and straightforwardly with generic text editors or (for images 4403 composed of pixels) generic paint programs or (for drawings) some 4404 widely available drawing editor, and that is suitable for input to 4405 text formatters or for automatic translation to a variety of 4406 formats suitable for input to text formatters. A copy made in an 4407 otherwise Transparent file format whose markup has been designed 4408 to thwart or discourage subsequent modification by readers is not 4409 Transparent. A copy that is not "Transparent" is called "Opaque." 4410 4411 Examples of suitable formats for Transparent copies include plain 4412 ASCII without markup, Texinfo input format, LaTeX input format, 4413 SGML or XML using a publicly available DTD, and 4414 standard-conforming simple HTML designed for human modification. 4415 Opaque formats include PostScript, PDF, proprietary formats that 4416 can be read and edited only by proprietary word processors, SGML 4417 or XML for which the DTD and/or processing tools are not generally 4418 available, and the machine-generated HTML produced by some word 4419 processors for output purposes only. 4420 4421 The "Title Page" means, for a printed book, the title page itself, 4422 plus such following pages as are needed to hold, legibly, the 4423 material this License requires to appear in the title page. For 4424 works in formats which do not have any title page as such, "Title 4425 Page" means the text near the most prominent appearance of the 4426 work's title, preceding the beginning of the body of the text. 4427 4428 2. VERBATIM COPYING 4429 4430 You may copy and distribute the Document in any medium, either 4431 commercially or noncommercially, provided that this License, the 4432 copyright notices, and the license notice saying this License 4433 applies to the Document are reproduced in all copies, and that you 4434 add no other conditions whatsoever to those of this License. You 4435 may not use technical measures to obstruct or control the reading 4436 or further copying of the copies you make or distribute. However, 4437 you may accept compensation in exchange for copies. If you 4438 distribute a large enough number of copies you must also follow 4439 the conditions in section 3. 4440 4441 You may also lend copies, under the same conditions stated above, 4442 and you may publicly display copies. 4443 4444 3. COPYING IN QUANTITY 4445 4446 If you publish printed copies of the Document numbering more than 4447 100, and the Document's license notice requires Cover Texts, you 4448 must enclose the copies in covers that carry, clearly and legibly, 4449 all these Cover Texts: Front-Cover Texts on the front cover, and 4450 Back-Cover Texts on the back cover. Both covers must also clearly 4451 and legibly identify you as the publisher of these copies. The 4452 front cover must present the full title with all words of the 4453 title equally prominent and visible. You may add other material 4454 on the covers in addition. Copying with changes limited to the 4455 covers, as long as they preserve the title of the Document and 4456 satisfy these conditions, can be treated as verbatim copying in 4457 other respects. 4458 4459 If the required texts for either cover are too voluminous to fit 4460 legibly, you should put the first ones listed (as many as fit 4461 reasonably) on the actual cover, and continue the rest onto 4462 adjacent pages. 4463 4464 If you publish or distribute Opaque copies of the Document 4465 numbering more than 100, you must either include a 4466 machine-readable Transparent copy along with each Opaque copy, or 4467 state in or with each Opaque copy a publicly-accessible 4468 computer-network location containing a complete Transparent copy 4469 of the Document, free of added material, which the general 4470 network-using public has access to download anonymously at no 4471 charge using public-standard network protocols. If you use the 4472 latter option, you must take reasonably prudent steps, when you 4473 begin distribution of Opaque copies in quantity, to ensure that 4474 this Transparent copy will remain thus accessible at the stated 4475 location until at least one year after the last time you 4476 distribute an Opaque copy (directly or through your agents or 4477 retailers) of that edition to the public. 4478 4479 It is requested, but not required, that you contact the authors of 4480 the Document well before redistributing any large number of 4481 copies, to give them a chance to provide you with an updated 4482 version of the Document. 4483 4484 4. MODIFICATIONS 4485 4486 You may copy and distribute a Modified Version of the Document 4487 under the conditions of sections 2 and 3 above, provided that you 4488 release the Modified Version under precisely this License, with 4489 the Modified Version filling the role of the Document, thus 4490 licensing distribution and modification of the Modified Version to 4491 whoever possesses a copy of it. In addition, you must do these 4492 things in the Modified Version: 4493 4494 A. Use in the Title Page (and on the covers, if any) a title 4495 distinct from that of the Document, and from those of previous 4496 versions (which should, if there were any, be listed in the 4497 History section of the Document). You may use the same title 4498 as a previous version if the original publisher of that version 4499 gives permission. 4500 B. List on the Title Page, as authors, one or more persons or 4501 entities responsible for authorship of the modifications in the 4502 Modified Version, together with at least five of the principal 4503 authors of the Document (all of its principal authors, if it 4504 has less than five). 4505 C. State on the Title page the name of the publisher of the 4506 Modified Version, as the publisher. 4507 D. Preserve all the copyright notices of the Document. 4508 E. Add an appropriate copyright notice for your modifications 4509 adjacent to the other copyright notices. 4510 F. Include, immediately after the copyright notices, a license 4511 notice giving the public permission to use the Modified Version 4512 under the terms of this License, in the form shown in the 4513 Addendum below. 4514 G. Preserve in that license notice the full lists of Invariant 4515 Sections and required Cover Texts given in the Document's 4516 license notice. 4517 H. Include an unaltered copy of this License. 4518 I. Preserve the section entitled "History", and its title, and add 4519 to it an item stating at least the title, year, new authors, and 4520 publisher of the Modified Version as given on the Title Page. 4521 If there is no section entitled "History" in the Document, 4522 create one stating the title, year, authors, and publisher of 4523 the Document as given on its Title Page, then add an item 4524 describing the Modified Version as stated in the previous 4525 sentence. 4526 J. Preserve the network location, if any, given in the Document for 4527 public access to a Transparent copy of the Document, and 4528 likewise the network locations given in the Document for 4529 previous versions it was based on. These may be placed in the 4530 "History" section. You may omit a network location for a work 4531 that was published at least four years before the Document 4532 itself, or if the original publisher of the version it refers 4533 to gives permission. 4534 K. In any section entitled "Acknowledgements" or "Dedications", 4535 preserve the section's title, and preserve in the section all the 4536 substance and tone of each of the contributor acknowledgements 4537 and/or dedications given therein. 4538 L. Preserve all the Invariant Sections of the Document, 4539 unaltered in their text and in their titles. Section numbers 4540 or the equivalent are not considered part of the section titles. 4541 M. Delete any section entitled "Endorsements." Such a section 4542 may not be included in the Modified Version. 4543 N. Do not retitle any existing section as "Endorsements" or to 4544 conflict in title with any Invariant Section. 4545 4546 If the Modified Version includes new front-matter sections or 4547 appendices that qualify as Secondary Sections and contain no 4548 material copied from the Document, you may at your option 4549 designate some or all of these sections as invariant. To do this, 4550 add their titles to the list of Invariant Sections in the Modified 4551 Version's license notice. These titles must be distinct from any 4552 other section titles. 4553 4554 You may add a section entitled "Endorsements", provided it contains 4555 nothing but endorsements of your Modified Version by various 4556 parties-for example, statements of peer review or that the text has 4557 been approved by an organization as the authoritative definition 4558 of a standard. 4559 4560 You may add a passage of up to five words as a Front-Cover Text, 4561 and a passage of up to 25 words as a Back-Cover Text, to the end 4562 of the list of Cover Texts in the Modified Version. Only one 4563 passage of Front-Cover Text and one of Back-Cover Text may be 4564 added by (or through arrangements made by) any one entity. If the 4565 Document already includes a cover text for the same cover, 4566 previously added by you or by arrangement made by the same entity 4567 you are acting on behalf of, you may not add another; but you may 4568 replace the old one, on explicit permission from the previous 4569 publisher that added the old one. 4570 4571 The author(s) and publisher(s) of the Document do not by this 4572 License give permission to use their names for publicity for or to 4573 assert or imply endorsement of any Modified Version. 4574 4575 5. COMBINING DOCUMENTS 4576 4577 You may combine the Document with other documents released under 4578 this License, under the terms defined in section 4 above for 4579 modified versions, provided that you include in the combination 4580 all of the Invariant Sections of all of the original documents, 4581 unmodified, and list them all as Invariant Sections of your 4582 combined work in its license notice. 4583 4584 The combined work need only contain one copy of this License, and 4585 multiple identical Invariant Sections may be replaced with a single 4586 copy. If there are multiple Invariant Sections with the same name 4587 but different contents, make the title of each such section unique 4588 by adding at the end of it, in parentheses, the name of the 4589 original author or publisher of that section if known, or else a 4590 unique number. Make the same adjustment to the section titles in 4591 the list of Invariant Sections in the license notice of the 4592 combined work. 4593 4594 In the combination, you must combine any sections entitled 4595 "History" in the various original documents, forming one section 4596 entitled "History"; likewise combine any sections entitled 4597 "Acknowledgements", and any sections entitled "Dedications." You 4598 must delete all sections entitled "Endorsements." 4599 4600 6. COLLECTIONS OF DOCUMENTS 4601 4602 You may make a collection consisting of the Document and other 4603 documents released under this License, and replace the individual 4604 copies of this License in the various documents with a single copy 4605 that is included in the collection, provided that you follow the 4606 rules of this License for verbatim copying of each of the 4607 documents in all other respects. 4608 4609 You may extract a single document from such a collection, and 4610 distribute it individually under this License, provided you insert 4611 a copy of this License into the extracted document, and follow 4612 this License in all other respects regarding verbatim copying of 4613 that document. 4614 4615 7. AGGREGATION WITH INDEPENDENT WORKS 4616 4617 A compilation of the Document or its derivatives with other 4618 separate and independent documents or works, in or on a volume of 4619 a storage or distribution medium, does not as a whole count as a 4620 Modified Version of the Document, provided no compilation 4621 copyright is claimed for the compilation. Such a compilation is 4622 called an "aggregate", and this License does not apply to the 4623 other self-contained works thus compiled with the Document, on 4624 account of their being thus compiled, if they are not themselves 4625 derivative works of the Document. 4626 4627 If the Cover Text requirement of section 3 is applicable to these 4628 copies of the Document, then if the Document is less than one 4629 quarter of the entire aggregate, the Document's Cover Texts may be 4630 placed on covers that surround only the Document within the 4631 aggregate. Otherwise they must appear on covers around the whole 4632 aggregate. 4633 4634 8. TRANSLATION 4635 4636 Translation is considered a kind of modification, so you may 4637 distribute translations of the Document under the terms of section 4638 4. Replacing Invariant Sections with translations requires special 4639 permission from their copyright holders, but you may include 4640 translations of some or all Invariant Sections in addition to the 4641 original versions of these Invariant Sections. You may include a 4642 translation of this License provided that you also include the 4643 original English version of this License. In case of a 4644 disagreement between the translation and the original English 4645 version of this License, the original English version will prevail. 4646 4647 9. TERMINATION 4648 4649 You may not copy, modify, sublicense, or distribute the Document 4650 except as expressly provided for under this License. Any other 4651 attempt to copy, modify, sublicense or distribute the Document is 4652 void, and will automatically terminate your rights under this 4653 License. However, parties who have received copies, or rights, 4654 from you under this License will not have their licenses 4655 terminated so long as such parties remain in full compliance. 4656 4657 10. FUTURE REVISIONS OF THIS LICENSE 4658 4659 The Free Software Foundation may publish new, revised versions of 4660 the GNU Free Documentation License from time to time. Such new 4661 versions will be similar in spirit to the present version, but may 4662 differ in detail to address new problems or concerns. See 4663 http://www.gnu.org/copyleft/. 4664 4665 Each version of the License is given a distinguishing version 4666 number. If the Document specifies that a particular numbered 4667 version of this License "or any later version" applies to it, you 4668 have the option of following the terms and conditions either of 4669 that specified version or of any later version that has been 4670 published (not as a draft) by the Free Software Foundation. If 4671 the Document does not specify a version number of this License, 4672 you may choose any version ever published (not as a draft) by the 4673 Free Software Foundation. 4674 4675 4676ADDENDUM: How to use this License for your documents 4677==================================================== 4678 4679To use this License in a document you have written, include a copy of 4680the License in the document and put the following copyright and license 4681notices just after the title page: 4682 4683 Copyright (C) YEAR YOUR NAME. 4684 Permission is granted to copy, distribute and/or modify this document 4685 under the terms of the GNU Free Documentation License, Version 1.1 4686 or any later version published by the Free Software Foundation; 4687 with the Invariant Sections being LIST THEIR TITLES, with the 4688 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. 4689 A copy of the license is included in the section entitled "GNU 4690 Free Documentation License." 4691 4692 If you have no Invariant Sections, write "with no Invariant Sections" 4693instead of saying which ones are invariant. If you have no Front-Cover 4694Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being 4695LIST"; likewise for Back-Cover Texts. 4696 4697 If your document contains nontrivial examples of program code, we 4698recommend releasing these examples in parallel under your choice of 4699free software license, such as the GNU General Public License, to 4700permit their use in free software. 4701 4702 4703File: standards.info, Node: Index, Prev: Copying This Manual, Up: Top 4704 4705Index 4706***** 4707 4708[index] 4709* Menu: 4710 4711* #endif, commenting: Comments. (line 54) 4712* --help option: Command-Line Interfaces. 4713 (line 119) 4714* --version option: Command-Line Interfaces. 4715 (line 34) 4716* -Wall compiler option: Syntactic Conventions. 4717 (line 10) 4718* accepting contributions: Contributions. (line 6) 4719* address for bug reports: Command-Line Interfaces. 4720 (line 125) 4721* ANSI C standard: Standard C. (line 6) 4722* arbitrary limits on data: Semantics. (line 6) 4723* autoconf: System Portability. (line 23) 4724* avoiding proprietary code: Reading Non-Free Code. 4725 (line 6) 4726* behavior, dependent on program's name: User Interfaces. (line 6) 4727* binary packages: Install Command Categories. 4728 (line 80) 4729* bindir: Directory Variables. (line 45) 4730* braces, in C source: Formatting. (line 6) 4731* bug reports: Command-Line Interfaces. 4732 (line 125) 4733* canonical name of a program: Command-Line Interfaces. 4734 (line 41) 4735* casting pointers to integers: CPU Portability. (line 67) 4736* change logs: Change Logs. (line 6) 4737* change logs, conditional changes: Conditional Changes. (line 6) 4738* change logs, style: Style of Change Logs. 4739 (line 6) 4740* command-line arguments, decoding: Semantics. (line 46) 4741* command-line interface: Command-Line Interfaces. 4742 (line 6) 4743* commenting: Comments. (line 6) 4744* compatibility with C and POSIX standards: Compatibility. (line 6) 4745* compiler warnings: Syntactic Conventions. 4746 (line 10) 4747* conditional changes, and change logs: Conditional Changes. (line 6) 4748* conditionals, comments for: Comments. (line 54) 4749* configure: Configuration. (line 6) 4750* control-L: Formatting. (line 114) 4751* conventions for makefiles: Makefile Conventions. 4752 (line 6) 4753* corba: Graphical Interfaces. 4754 (line 16) 4755* credits for manuals: Manual Credits. (line 6) 4756* data types, and portability: CPU Portability. (line 6) 4757* declaration for system functions: System Functions. (line 21) 4758* documentation: Documentation. (line 6) 4759* doschk: Names. (line 38) 4760* downloading this manual: Preface. (line 17) 4761* error messages: Semantics. (line 19) 4762* error messages, formatting: Errors. (line 6) 4763* exec_prefix: Directory Variables. (line 27) 4764* expressions, splitting: Formatting. (line 77) 4765* file usage: File Usage. (line 6) 4766* file-name limitations: Names. (line 38) 4767* formatting error messages: Errors. (line 6) 4768* formatting source code: Formatting. (line 6) 4769* formfeed: Formatting. (line 114) 4770* function argument, declaring: Syntactic Conventions. 4771 (line 6) 4772* function prototypes: Standard C. (line 17) 4773* getopt: Command-Line Interfaces. 4774 (line 6) 4775* gettext: Internationalization. 4776 (line 6) 4777* gnome: Graphical Interfaces. 4778 (line 16) 4779* graphical user interface: Graphical Interfaces. 4780 (line 6) 4781* gtk: Graphical Interfaces. 4782 (line 6) 4783* GUILE: Source Language. (line 38) 4784* implicit int: Syntactic Conventions. 4785 (line 6) 4786* impossible conditions: Semantics. (line 70) 4787* internationalization: Internationalization. 4788 (line 6) 4789* legal aspects: Legal Issues. (line 6) 4790* legal papers: Contributions. (line 6) 4791* libexecdir: Directory Variables. (line 58) 4792* libraries: Libraries. (line 6) 4793* library functions, and portability: System Functions. (line 6) 4794* license for manuals: License for Manuals. (line 6) 4795* lint: Syntactic Conventions. 4796 (line 109) 4797* long option names: Option Table. (line 6) 4798* long-named options: Command-Line Interfaces. 4799 (line 12) 4800* makefile, conventions for: Makefile Conventions. 4801 (line 6) 4802* malloc return value: Semantics. (line 25) 4803* man pages: Man Pages. (line 6) 4804* manual structure: Manual Structure Details. 4805 (line 6) 4806* memory allocation failure: Semantics. (line 25) 4807* memory usage: Memory Usage. (line 6) 4808* message text, and internationalization: Internationalization. 4809 (line 29) 4810* mmap: Mmap. (line 6) 4811* multiple variables in a line: Syntactic Conventions. 4812 (line 35) 4813* names of variables, functions, and files: Names. (line 6) 4814* NEWS file: NEWS File. (line 6) 4815* non-POSIX systems, and portability: System Portability. (line 32) 4816* non-standard extensions: Using Extensions. (line 6) 4817* NUL characters: Semantics. (line 11) 4818* open brace: Formatting. (line 6) 4819* optional features, configure-time: Configuration. (line 76) 4820* options for compatibility: Compatibility. (line 14) 4821* output device and program's behavior: User Interfaces. (line 13) 4822* packaging: Releases. (line 6) 4823* portability, and data types: CPU Portability. (line 6) 4824* portability, and library functions: System Functions. (line 6) 4825* portability, between system types: System Portability. (line 6) 4826* POSIX compatibility: Compatibility. (line 6) 4827* POSIXLY_CORRECT, environment variable: Compatibility. (line 21) 4828* post-installation commands: Install Command Categories. 4829 (line 6) 4830* pre-installation commands: Install Command Categories. 4831 (line 6) 4832* prefix: Directory Variables. (line 17) 4833* program configuration: Configuration. (line 6) 4834* program design: Design Advice. (line 6) 4835* program name and its behavior: User Interfaces. (line 6) 4836* program's canonical name: Command-Line Interfaces. 4837 (line 41) 4838* programming languges: Source Language. (line 6) 4839* proprietary programs: Reading Non-Free Code. 4840 (line 6) 4841* README file: Releases. (line 17) 4842* references to non-free material: References. (line 6) 4843* releasing: Managing Releases. (line 6) 4844* sbindir: Directory Variables. (line 51) 4845* signal handling: Semantics. (line 59) 4846* spaces before open-paren: Formatting. (line 71) 4847* standard command-line options: Command-Line Interfaces. 4848 (line 31) 4849* standards for makefiles: Makefile Conventions. 4850 (line 6) 4851* string library functions: System Functions. (line 55) 4852* syntactic conventions: Syntactic Conventions. 4853 (line 6) 4854* table of long options: Option Table. (line 6) 4855* temporary files: Semantics. (line 84) 4856* temporary variables: Syntactic Conventions. 4857 (line 23) 4858* texinfo.tex, in a distribution: Releases. (line 73) 4859* TMPDIR environment variable: Semantics. (line 84) 4860* trademarks: Trademarks. (line 6) 4861* where to obtain standards.texi: Preface. (line 17) 4862 4863 4864 4865Tag Table: 4866Node: Top696 4867Node: Preface1396 4868Node: Legal Issues3616 4869Node: Reading Non-Free Code4080 4870Node: Contributions5808 4871Node: Trademarks7962 4872Node: Design Advice9025 4873Node: Source Language9609 4874Node: Compatibility11621 4875Node: Using Extensions13249 4876Node: Standard C14825 4877Node: Conditional Compilation17228 4878Node: Program Behavior18527 4879Node: Semantics19446 4880Node: Libraries24139 4881Node: Errors25384 4882Node: User Interfaces27165 4883Node: Graphical Interfaces28770 4884Node: Command-Line Interfaces29805 4885Node: Option Table35876 4886Node: Memory Usage50885 4887Node: File Usage51910 4888Node: Writing C52658 4889Node: Formatting53508 4890Node: Comments57571 4891Node: Syntactic Conventions60873 4892Node: Names64285 4893Node: System Portability66494 4894Node: CPU Portability68879 4895Node: System Functions72135 4896Node: Internationalization77332 4897Node: Mmap80485 4898Node: Documentation81195 4899Node: GNU Manuals82300 4900Node: Doc Strings and Manuals87357 4901Node: Manual Structure Details88910 4902Node: License for Manuals90328 4903Node: Manual Credits91302 4904Node: Printed Manuals91695 4905Node: NEWS File92381 4906Node: Change Logs93059 4907Node: Change Log Concepts93813 4908Node: Style of Change Logs95677 4909Node: Simple Changes97712 4910Node: Conditional Changes98956 4911Node: Indicating the Part Changed100378 4912Node: Man Pages100905 4913Node: Reading other Manuals102529 4914Node: Managing Releases103320 4915Node: Configuration104083 4916Node: Makefile Conventions110988 4917Node: Makefile Basics111794 4918Node: Utilities in Makefiles114968 4919Node: Command Variables117113 4920Node: Directory Variables120690 4921Node: Standard Targets131584 4922Ref: Standard Targets-Footnote-1142824 4923Node: Install Command Categories142924 4924Node: Releases147506 4925Node: References151594 4926Node: Copying This Manual153879 4927Node: GNU Free Documentation License154115 4928Node: Index173816 4929 4930End Tag Table 4931