grep.texi revision 131554
1\input texinfo @c -*-texinfo-*- 2@c %**start of header 3@setfilename grep.info 4@settitle grep, print lines matching a pattern 5@c %**end of header 6 7@c This file has the new style title page commands. 8@c Run `makeinfo' rather than `texinfo-format-buffer'. 9 10@c smallbook 11 12@c tex 13@c \overfullrule=0pt 14@c end tex 15 16@include version.texi 17 18@c Combine indices. 19@syncodeindex ky cp 20@syncodeindex pg cp 21@syncodeindex tp cp 22 23@defcodeindex op 24@syncodeindex op fn 25@syncodeindex vr fn 26 27@ifinfo 28@direntry 29* grep: (grep). print lines matching a pattern. 30@end direntry 31This file documents @command{grep}, a pattern matching engine. 32 33 34Published by the Free Software Foundation, 3559 Temple Place - Suite 330 36Boston, MA 02111-1307, USA 37 38@c man begin COPYRIGHT 39Copyright @copyright{} 2000, 2001 Free Software Foundation, Inc. 40 41Permission is granted to make and distribute verbatim copies of 42this manual provided the copyright notice and this permission notice 43are preserved on all copies. 44 45@ignore 46Permission is granted to process this file through TeX and print the 47results, provided the printed document carries a copying permission 48notice identical to this one except for the removal of this paragraph 49(this paragraph not being relevant to the printed manual). 50 51@end ignore 52Permission is granted to copy, distribute and/or modify this document 53under the terms of the GNU Free Documentation License, Version 1.1 or 54any later version published by the Free Software Foundation; with the 55Invariant Sections being ``GNU General Public License'' and ``GNU Free 56Documentation License'', with no Front-Cover Texts, and with no 57Back-Cover Texts. A copy of the license is included in the section 58entitled ``GNU Free Documentation License'' (@pxref{Copying}). 59@c man end 60@end ifinfo 61 62@setchapternewpage off 63 64@titlepage 65@title grep, searching for a pattern 66@subtitle version @value{VERSION}, @value{UPDATED} 67@author Alain Magloire et al. 68 69@page 70@vskip 0pt plus 1filll 71Copyright @copyright{} 2000, 2001 Free Software Foundation, Inc. 72 73@sp 2 74Published by the Free Software Foundation, @* 7559 Temple Place - Suite 330, @* 76Boston, MA 02111-1307, USA 77 78Permission is granted to copy, distribute and/or modify this document 79under the terms of the GNU Free Documentation License, Version 1.1 or 80any later version published by the Free Software Foundation; with the 81Invariant Sections being ``GNU General Public License'' and ``GNU Free 82Documentation License'', with no Front-Cover Texts, and with no 83Back-Cover Texts. A copy of the license is included in the section 84entitled ``GNU Free Documentation License''. 85@end titlepage 86 87 88@ifnottex 89@node Top 90@top Grep 91 92@command{grep} searches for lines matching a pattern. 93 94This document was produced for version @value{VERSION} of @sc{gnu} 95@command{grep}. 96@end ifnottex 97 98@menu 99* Introduction:: Introduction. 100* Invoking:: Invoking @command{grep}; description of options. 101* Diagnostics:: Exit status returned by @command{grep}. 102* Grep Programs:: @command{grep} programs. 103* Regular Expressions:: Regular Expressions. 104* Usage:: Examples. 105* Reporting Bugs:: Reporting Bugs. 106* Copying:: License terms. 107* Concept Index:: A menu with all the topics in this manual. 108* Index:: A menu with all @command{grep} commands 109 and command-line options. 110@end menu 111 112 113@node Introduction, Invoking, Top, Top 114@chapter Introduction 115 116@cindex Searching for a pattern. 117 118@command{grep} searches the input files 119for lines containing a match to a given 120pattern list. When it finds a match in a line, it copies the line to standard 121output (by default), or does whatever other sort of output you have requested 122with options. 123 124Though @command{grep} expects to do the matching on text, 125it has no limits on input line length other than available memory, 126and it can match arbitrary characters within a line. 127If the final byte of an input file is not a newline, 128@command{grep} silently supplies one. 129Since newline is also a separator for the list of patterns, there 130is no way to match newline characters in a text. 131 132@node Invoking 133@chapter Invoking @command{grep} 134 135@command{grep} comes with a rich set of options from @sc{posix.2} and @sc{gnu} 136extensions. 137 138@table @samp 139 140@item -c 141@itemx --count 142@opindex -c 143@opindex --count 144@cindex counting lines 145Suppress normal output; instead print a count of matching 146lines for each input file. With the @samp{-v}, @samp{--invert-match} option, 147count non-matching lines. 148 149@item -e @var{pattern} 150@itemx --regexp=@var{pattern} 151@opindex -e 152@opindex --regexp=@var{pattern} 153@cindex pattern list 154Use @var{pattern} as the pattern; useful to protect patterns 155beginning with a @samp{-}. 156 157@item -f @var{file} 158@itemx --file=@var{file} 159@opindex -f 160@opindex --file 161@cindex pattern from file 162Obtain patterns from @var{file}, one per line. The empty 163file contains zero patterns, and therefore matches nothing. 164 165@item -i 166@itemx --ignore-case 167@opindex -i 168@opindex --ignore-case 169@cindex case insensitive search 170Ignore case distinctions in both the pattern and the input files. 171 172@item -l 173@itemx --files-with-matches 174@opindex -l 175@opindex --files-with-matches 176@cindex names of matching files 177Suppress normal output; instead print the name of each input 178file from which output would normally have been printed. 179The scanning of every file will stop on the first match. 180 181@item -n 182@itemx --line-number 183@opindex -n 184@opindex --line-number 185@cindex line numbering 186Prefix each line of output with the line number within its input file. 187 188@item -o 189@itemx --only-matching 190@opindex -o 191@opindex --only-matching 192@cindex only matching 193Print only the part of matching lines that actually matches @var{pattern}. 194 195@item -q 196@itemx --quiet 197@itemx --silent 198@opindex -q 199@opindex --quiet 200@opindex --silent 201@cindex quiet, silent 202Quiet; do not write anything to standard output. Exit immediately with 203zero status if any match is found, even if an error was detected. Also 204see the @samp{-s} or @samp{--no-messages} option. 205 206@item -s 207@itemx --no-messages 208@opindex -s 209@opindex --no-messages 210@cindex suppress error messages 211Suppress error messages about nonexistent or unreadable files. 212Portability note: unlike @sc{gnu} @command{grep}, traditional 213@command{grep} did not conform to @sc{posix.2}, because traditional 214@command{grep} lacked a @samp{-q} option and its @samp{-s} option behaved 215like @sc{gnu} @command{grep}'s @samp{-q} option. Shell scripts intended 216to be portable to traditional @command{grep} should avoid both 217@samp{-q} and @samp{-s} and should redirect 218output to @file{/dev/null} instead. 219 220@item -v 221@itemx --invert-match 222@opindex -v 223@opindex --invert-match 224@cindex invert matching 225@cindex print non-matching lines 226Invert the sense of matching, to select non-matching lines. 227 228@item -x 229@itemx --line-regexp 230@opindex -x 231@opindex --line-regexp 232@cindex match the whole line 233Select only those matches that exactly match the whole line. 234 235@end table 236 237@section @sc{gnu} Extensions 238 239@table @samp 240 241@item -A @var{num} 242@itemx --after-context=@var{num} 243@opindex -A 244@opindex --after-context 245@cindex after context 246@cindex context lines, after match 247Print @var{num} lines of trailing context after matching lines. 248 249@item -B @var{num} 250@itemx --before-context=@var{num} 251@opindex -B 252@opindex --before-context 253@cindex before context 254@cindex context lines, before match 255Print @var{num} lines of leading context before matching lines. 256 257@item -C @var{num} 258@itemx --context=@var{num} 259@opindex -C 260@opindex --context 261@cindex context 262Print @var{num} lines of output context. 263 264@item --colour[=@var{WHEN}] 265@itemx --color[=@var{WHEN}] 266@opindex --colour 267@cindex highlight, color, colour 268The matching string is surrounded by the marker specify in @var{GREP_COLOR}. 269@var{WHEN} may be `never', `always', or `auto'. 270 271@item -@var{num} 272@opindex -NUM 273Same as @samp{--context=@var{num}} lines of leading and trailing 274context. However, grep will never print any given line more than once. 275 276 277@item -V 278@itemx --version 279@opindex -V 280@opindex --version 281@cindex Version, printing 282Print the version number of @command{grep} to the standard output stream. 283This version number should be included in all bug reports. 284 285@item --help 286@opindex --help 287@cindex Usage summary, printing 288Print a usage message briefly summarizing these command-line options 289and the bug-reporting address, then exit. 290 291@itemx --binary-files=@var{type} 292@opindex --binary-files 293@cindex binary files 294If the first few bytes of a file indicate that the file contains binary 295data, assume that the file is of type @var{type}. By default, 296@var{type} is @samp{binary}, and @command{grep} normally outputs either 297a one-line message saying that a binary file matches, or no message if 298there is no match. If @var{type} is @samp{without-match}, 299@command{grep} assumes that a binary file does not match; 300this is equivalent to the @samp{-I} option. If @var{type} 301is @samp{text}, @command{grep} processes a binary file as if it were 302text; this is equivalent to the @samp{-a} option. 303@emph{Warning:} @samp{--binary-files=text} might output binary garbage, 304which can have nasty side effects if the output is a terminal and if the 305terminal driver interprets some of it as commands. 306 307@item -b 308@itemx --byte-offset 309@opindex -b 310@opindex --byte-offset 311@cindex byte offset 312Print the byte offset within the input file before each line of output. 313When @command{grep} runs on @sc{ms-dos} or MS-Windows, the printed 314byte offsets 315depend on whether the @samp{-u} (@samp{--unix-byte-offsets}) option is 316used; see below. 317 318@item -D @var{action} 319@itemx --devices=@var{action} 320@opindex -D 321@opindex --devices 322@cindex device search 323If an input file is a device, FIFO or socket, use @var{action} to process it. 324By default, @var{action} is @samp{read}, which means that devices are 325read just as if they were ordinary files. 326If @var{action} is @samp{skip}, devices, FIFOs and sockets are silently 327skipped. 328 329@item -d @var{action} 330@itemx --directories=@var{action} 331@opindex -d 332@opindex --directories 333@cindex directory search 334If an input file is a directory, use @var{action} to process it. 335By default, @var{action} is @samp{read}, which means that directories are 336read just as if they were ordinary files (some operating systems 337and filesystems disallow this, and will cause @command{grep} to print error 338messages for every directory or silently skip them). If @var{action} is 339@samp{skip}, directories are silently skipped. If @var{action} is 340@samp{recurse}, @command{grep} reads all files under each directory, 341recursively; this is equivalent to the @samp{-r} option. 342 343@item -H 344@itemx --with-filename 345@opindex -H 346@opindex --With-filename 347@cindex with filename prefix 348Print the filename for each match. 349 350@item -h 351@itemx --no-filename 352@opindex -h 353@opindex --no-filename 354@cindex no filename prefix 355Suppress the prefixing of filenames on output when multiple files are searched. 356 357@item --line-buffered 358@opindex --line-buffered 359@cindex line buffering 360Set the line buffering policy, this can be a performance penality. 361 362@item --label=@var{LABEL} 363@opindex --label 364@cindex changing name of standard input 365Displays input actually coming from standard input as input coming from file 366@var{LABEL}. This is especially useful for tools like zgrep, e.g. 367@command{gzip -cd foo.gz |grep --label=foo something} 368 369@item -L 370@itemx --files-without-match 371@opindex -L 372@opindex --files-without-match 373@cindex files which don't match 374Suppress normal output; instead print the name of each input 375file from which no output would normally have been printed. 376The scanning of every file will stop on the first match. 377 378@item -a 379@itemx --text 380@opindex -a 381@opindex --text 382@cindex suppress binary data 383@cindex binary files 384Process a binary file as if it were text; this is equivalent to the 385@samp{--binary-files=text} option. 386 387@item -I 388Process a binary file as if it did not contain matching data; this is 389equivalent to the @samp{--binary-files=without-match} option. 390 391@item -w 392@itemx --word-regexp 393@opindex -w 394@opindex --word-regexp 395@cindex matching whole words 396Select only those lines containing matches that form 397whole words. The test is that the matching substring 398must either be at the beginning of the line, or preceded 399by a non-word constituent character. Similarly, 400it must be either at the end of the line or followed by 401a non-word constituent character. Word-constituent 402characters are letters, digits, and the underscore. 403 404@item -r 405@itemx -R 406@itemx --recursive 407@opindex -r 408@opindex --recursive 409@cindex recursive search 410@cindex searching directory trees 411For each directory mentioned in the command line, read and process all 412files in that directory, recursively. This is the same as the 413@samp{--directories=recurse} option. 414 415@item --include=@var{file_pattern} 416@opindex --include 417@cindex include files 418@cindex searching directory trees 419When processing directories recursively, only files matching @var{file_pattern} 420will be search. 421 422@item --exclude=@var{file_pattern} 423@opindex --exclude 424@cindex exclude files 425@cindex searching directory trees 426When processing directories recursively, skip files matching @var{file_pattern}. 427 428@item -m @var{num} 429@itemx --max-count=@var{num} 430@opindex -m 431@opindex --max-count 432@cindex max-count 433Stop reading a file after @var{num} matching lines. If the input is 434standard input from a regular file, and @var{num} matching lines are 435output, @command{grep} ensures that the standard input is positioned to 436just after the last matching line before exiting, regardless of the 437presence of trailing context lines. This enables a calling process 438to resume a search. For example, the following shell script makes use 439of it: 440 441@example 442while grep -m 1 PATTERN 443do 444 echo xxxx 445done < FILE 446@end example 447 448But the following probably will not work because a pipe is not a regular 449file: 450 451@example 452# This probably will not work. 453cat FILE | 454while grep -m 1 PATTERN 455do 456 echo xxxx 457done 458@end example 459 460When @command{grep} stops after NUM matching lines, it outputs 461any trailing context lines. Since context does not include matching 462lines, @command{grep} will stop when it encounters another matching line. 463When the @samp{-c} or @samp{--count} option is also used, 464@command{grep} does not output a count greater than @var{num}. 465When the @samp{-v} or @samp{--invert-match} option is 466also used, @command{grep} stops after outputting @var{num} 467non-matching lines. 468 469@item -y 470@opindex -y 471@cindex case insensitive search, obsolete option 472Obsolete synonym for @samp{-i}. 473 474@item -U 475@itemx --binary 476@opindex -U 477@opindex --binary 478@cindex DOS/Windows binary files 479@cindex binary files, DOS/Windows 480Treat the file(s) as binary. By default, under @sc{ms-dos} 481and MS-Windows, @command{grep} guesses the file type by looking 482at the contents of the first 32kB read from the file. 483If @command{grep} decides the file is a text file, it strips the 484@code{CR} characters from the original file contents (to make 485regular expressions with @code{^} and @code{$} work correctly). 486Specifying @samp{-U} overrules this guesswork, causing all 487files to be read and passed to the matching mechanism 488verbatim; if the file is a text file with @code{CR/LF} pairs 489at the end of each line, this will cause some regular 490expressions to fail. This option has no effect on platforms other than 491@sc{ms-dos} and MS-Windows. 492 493@item -u 494@itemx --unix-byte-offsets 495@opindex -u 496@opindex --unix-byte-offsets 497@cindex DOS byte offsets 498@cindex byte offsets, on DOS/Windows 499Report Unix-style byte offsets. This switch causes 500@command{grep} to report byte offsets as if the file were Unix style 501text file, i.e., the byte offsets ignore the @code{CR} characters which were 502stripped. This will produce results identical to running @command{grep} on 503a Unix machine. This option has no effect unless @samp{-b} 504option is also used; it has no effect on platforms other than @sc{ms-dos} and 505MS-Windows. 506 507@item --mmap 508@opindex --mmap 509@cindex memory mapped input 510If possible, use the @code{mmap} system call to read input, instead of 511the default @code{read} system call. In some situations, @samp{--mmap} 512yields better performance. However, @samp{--mmap} can cause undefined 513behavior (including core dumps) if an input file shrinks while 514@command{grep} is operating, or if an I/O error occurs. 515 516@item -Z 517@itemx --null 518@opindex -Z 519@opindex --null 520@cindex zero-terminated file names 521Output a zero byte (the @sc{ascii} @code{NUL} character) instead of the 522character that normally follows a file name. For example, @samp{grep 523-lZ} outputs a zero byte after each file name instead of the usual 524newline. This option makes the output unambiguous, even in the presence 525of file names containing unusual characters like newlines. This option 526can be used with commands like @samp{find -print0}, @samp{perl -0}, 527@samp{sort -z}, and @samp{xargs -0} to process arbitrary file names, 528even those that contain newline characters. 529 530@item -z 531@itemx --null-data 532@opindex -z 533@opindex --null-data 534@cindex zero-terminated lines 535Treat the input as a set of lines, each terminated by a zero byte (the 536@sc{ascii} @code{NUL} character) instead of a newline. Like the @samp{-Z} 537or @samp{--null} option, this option can be used with commands like 538@samp{sort -z} to process arbitrary file names. 539 540@end table 541 542Several additional options control which variant of the @command{grep} 543matching engine is used. @xref{Grep Programs}. 544 545@section Environment Variables 546 547Grep's behavior is affected by the following environment variables. 548 549A locale @code{LC_@var{foo}} is specified by examining the three 550environment variables @env{LC_ALL}, @env{LC_@var{foo}}, and @env{LANG}, 551in that order. The first of these variables that is set specifies the 552locale. For example, if @env{LC_ALL} is not set, but @env{LC_MESSAGES} 553is set to @samp{pt_BR}, then Brazilian Portuguese is used for the 554@code{LC_MESSAGES} locale. The C locale is used if none of these 555environment variables are set, or if the locale catalog is not 556installed, or if @command{grep} was not compiled with national language 557support (@sc{nls}). 558 559@cindex environment variables 560 561@table @env 562 563@item GREP_OPTIONS 564@vindex GREP_OPTIONS 565@cindex default options environment variable 566This variable specifies default options to be placed in front of any 567explicit options. For example, if @code{GREP_OPTIONS} is 568@samp{--binary-files=without-match --directories=skip}, @command{grep} 569behaves as if the two options @samp{--binary-files=without-match} and 570@samp{--directories=skip} had been specified before 571any explicit options. Option specifications are separated by 572whitespace. A backslash escapes the next character, so it can be used to 573specify an option containing whitespace or a backslash. 574 575@item GREP_COLOR 576@vindex GREP_COLOR 577@cindex highlight markers 578This variable specifies the surrounding markers use to highlight the matching 579text. The default is control ascii red. 580 581@item LC_ALL 582@itemx LC_COLLATE 583@itemx LANG 584@vindex LC_ALL 585@vindex LC_COLLATE 586@vindex LANG 587@cindex character type 588@cindex national language support 589@cindex NLS 590These variables specify the @code{LC_COLLATE} locale, which determines 591the collating sequence used to interpret range expressions like 592@samp{[a-z]}. 593 594@item LC_ALL 595@itemx LC_CTYPE 596@itemx LANG 597@vindex LC_ALL 598@vindex LC_CTYPE 599@vindex LANG 600@cindex character type 601@cindex national language support 602@cindex NLS 603These variables specify the @code{LC_CTYPE} locale, which determines the 604type of characters, e.g., which characters are whitespace. 605 606@item LC_ALL 607@itemx LC_MESSAGES 608@itemx LANG 609@vindex LC_ALL 610@vindex LC_MESSAGES 611@vindex LANG 612@cindex language of messages 613@cindex message language 614@cindex national language support 615@cindex NLS 616@cindex translation of message language 617These variables specify the @code{LC_MESSAGES} locale, which determines 618the language that @command{grep} uses for messages. The default C 619locale uses American English messages. 620 621@item POSIXLY_CORRECT 622@vindex POSIXLY_CORRECT 623If set, @command{grep} behaves as @sc{posix.2} requires; otherwise, 624@command{grep} behaves more like other @sc{gnu} programs. @sc{posix.2} 625requires that options that 626follow file names must be treated as file names; by default, such 627options are permuted to the front of the operand list and are treated as 628options. Also, @sc{posix.2} requires that unrecognized options be 629diagnosed as 630``illegal'', but since they are not really against the law the default 631is to diagnose them as ``invalid''. @code{POSIXLY_CORRECT} also 632disables @code{_@var{N}_GNU_nonoption_argv_flags_}, described below. 633 634@item _@var{N}_GNU_nonoption_argv_flags_ 635@vindex _@var{N}_GNU_nonoption_argv_flags_ 636(Here @code{@var{N}} is @command{grep}'s numeric process ID.) If the 637@var{i}th character of this environment variable's value is @samp{1}, do 638not consider the @var{i}th operand of @command{grep} to be an option, even if 639it appears to be one. A shell can put this variable in the environment 640for each command it runs, specifying which operands are the results of 641file name wildcard expansion and therefore should not be treated as 642options. This behavior is available only with the @sc{gnu} C library, and 643only when @code{POSIXLY_CORRECT} is not set. 644 645@end table 646 647@node Diagnostics 648@chapter Diagnostics 649 650Normally, exit status is 0 if selected lines are found and 1 otherwise. 651But the exit status is 2 if an error occurred, unless the @option{-q} or 652@option{--quiet} or @option{--silent} option is used and a selected line 653is found. 654 655@node Grep Programs 656@chapter @command{grep} programs 657 658@command{grep} searches the named input files (or standard input if no 659files are named, or the file name @file{-} is given) for lines containing 660a match to the given pattern. By default, @command{grep} prints the 661matching lines. There are four major variants of @command{grep}, 662controlled by the following options. 663 664@table @samp 665 666@item -G 667@itemx --basic-regexp 668@opindex -G 669@opindex --basic-regexp 670@cindex matching basic regular expressions 671Interpret the pattern as a basic regular expression. This is the default. 672 673@item -E 674@itemx --extended-regexp 675@opindex -E 676@opindex --extended-regexp 677@cindex matching extended regular expressions 678Interpret the pattern as an extended regular expression. 679 680@item -F 681@itemx --fixed-strings 682@opindex -F 683@opindex --fixed-strings 684@cindex matching fixed strings 685Interpret the pattern as a list of fixed strings, separated 686by newlines, any of which is to be matched. 687 688@item -P 689@itemx --perl-regexp 690@opindex -P 691@opindex --perl-regexp 692@cindex matching Perl regular expressions 693Interpret the pattern as a Perl regular expression. 694 695@end table 696 697In addition, two variant programs @sc{egrep} and @sc{fgrep} are available. 698@sc{egrep} is the same as @samp{grep -E}. @sc{fgrep} is the 699same as @samp{grep -F}. 700 701@node Regular Expressions 702@chapter Regular Expressions 703@cindex regular expressions 704 705A @dfn{regular expression} is a pattern that describes a set of strings. 706Regular expressions are constructed analogously to arithmetic expressions, 707by using various operators to combine smaller expressions. 708@command{grep} understands two different versions of regular expression 709syntax: ``basic''(BRE) and ``extended''(ERE). In @sc{gnu} @command{grep}, 710there is no difference in available functionality using either syntax. 711In other implementations, basic regular expressions are less powerful. 712The following description applies to extended regular expressions; 713differences for basic regular expressions are summarized afterwards. 714 715The fundamental building blocks are the regular expressions that match 716a single character. Most characters, including all letters and digits, 717are regular expressions that match themselves. Any metacharacter 718with special meaning may be quoted by preceding it with a backslash. 719 720A regular expression may be followed by one of several 721repetition operators: 722 723@table @samp 724 725@item . 726@opindex . 727@cindex dot 728@cindex period 729The period @samp{.} matches any single character. 730 731@item ? 732@opindex ? 733@cindex question mark 734@cindex match sub-expression at most once 735The preceding item is optional and will be matched at most once. 736 737@item * 738@opindex * 739@cindex asterisk 740@cindex match sub-expression zero or more times 741The preceding item will be matched zero or more times. 742 743@item + 744@opindex + 745@cindex plus sign 746The preceding item will be matched one or more times. 747 748@item @{@var{n}@} 749@opindex @{n@} 750@cindex braces, one argument 751@cindex match sub-expression n times 752The preceding item is matched exactly @var{n} times. 753 754@item @{@var{n},@} 755@opindex @{n,@} 756@cindex braces, second argument omitted 757@cindex match sub-expression n or more times 758The preceding item is matched n or more times. 759 760@item @{@var{n},@var{m}@} 761@opindex @{n,m@} 762@cindex braces, two arguments 763The preceding item is matched at least @var{n} times, but not more than 764@var{m} times. 765 766@end table 767 768Two regular expressions may be concatenated; the resulting regular 769expression matches any string formed by concatenating two substrings 770that respectively match the concatenated subexpressions. 771 772Two regular expressions may be joined by the infix operator @samp{|}; the 773resulting regular expression matches any string matching either subexpression. 774 775Repetition takes precedence over concatenation, which in turn 776takes precedence over alternation. A whole subexpression may be 777enclosed in parentheses to override these precedence rules. 778 779@section Character Class 780 781@cindex bracket expression 782@cindex character class 783A @dfn{bracket expression} is a list of characters enclosed by @samp{[} and 784@samp{]}. It matches any single character in that list; if the first 785character of the list is the caret @samp{^}, then it matches any character 786@strong{not} in the list. For example, the regular expression 787@samp{[0123456789]} matches any single digit. 788 789@cindex range expression 790Within a bracket expression, a @dfn{range expression} consists of two 791characters separated by a hyphen. It matches any single character that 792sorts between the two characters, inclusive, using the locale's 793collating sequence and character set. For example, in the default C 794locale, @samp{[a-d]} is equivalent to @samp{[abcd]}. Many locales sort 795characters in dictionary order, and in these locales @samp{[a-d]} is 796typically not equivalent to @samp{[abcd]}; it might be equivalent to 797@samp{[aBbCcDd]}, for example. To obtain the traditional interpretation 798of bracket expressions, you can use the C locale by setting the 799@env{LC_ALL} environment variable to the value @samp{C}. 800 801Finally, certain named classes of characters are predefined within 802bracket expressions, as follows. 803Their interpretation depends on the @code{LC_CTYPE} locale; the 804interpretation below is that of the C locale, which is the default 805if no @code{LC_CTYPE} locale is specified. 806 807@cindex classes of characters 808@cindex character classes 809@table @samp 810 811@item [:alnum:] 812@opindex alnum 813@cindex alphanumeric characters 814Alphanumeric characters: 815@samp{[:alpha:]} and @samp{[:digit:]}. 816 817@item [:alpha:] 818@opindex alpha 819@cindex alphabetic characters 820Alphabetic characters: 821@samp{[:lower:]} and @samp{[:upper:]}. 822 823@item [:blank:] 824@opindex blank 825@cindex blank characters 826Blank characters: 827space and tab. 828 829@item [:cntrl:] 830@opindex cntrl 831@cindex control characters 832Control characters. In @sc{ascii}, these characters have octal codes 000 833through 037, and 177 (@code{DEL}). In other character sets, these are 834the equivalent characters, if any. 835 836@item [:digit:] 837@opindex digit 838@cindex digit characters 839@cindex numeric characters 840Digits: @code{0 1 2 3 4 5 6 7 8 9}. 841 842@item [:graph:] 843@opindex graph 844@cindex graphic characters 845Graphical characters: 846@samp{[:alnum:]} and @samp{[:punct:]}. 847 848@item [:lower:] 849@opindex lower 850@cindex lower-case letters 851Lower-case letters: 852@code{a b c d e f g h i j k l m n o p q r s t u v w x y z}. 853 854@item [:print:] 855@opindex print 856@cindex printable characters 857Printable characters: 858@samp{[:alnum:]}, @samp{[:punct:]}, and space. 859 860@item [:punct:] 861@opindex punct 862@cindex punctuation characters 863Punctuation characters: 864@code{!@: " # $ % & ' ( ) * + , - .@: / : ; < = > ?@: @@ [ \ ] ^ _ ` @{ | @} ~}. 865 866@item [:space:] 867@opindex space 868@cindex space characters 869@cindex whitespace characters 870Space characters: 871tab, newline, vertical tab, form feed, carriage return, and space. 872 873@item [:upper:] 874@opindex upper 875@cindex upper-case letters 876Upper-case letters: 877@code{A B C D E F G H I J K L M N O P Q R S T U V W X Y Z}. 878 879@item [:xdigit:] 880@opindex xdigit 881@cindex xdigit class 882@cindex hexadecimal digits 883Hexadecimal digits: 884@code{0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f}. 885 886@end table 887For example, @samp{[[:alnum:]]} means @samp{[0-9A-Za-z]}, except the latter 888depends upon the C locale and the @sc{ascii} character 889encoding, whereas the former is independent of locale and character set. 890(Note that the brackets in these class names are 891part of the symbolic names, and must be included in addition to 892the brackets delimiting the bracket list.) 893 894Most metacharacters lose their special meaning inside lists. 895 896@table @samp 897@item ] 898ends the list if it's not the first list item. So, if you want to make 899the @samp{]} character a list item, you must put it first. 900 901@item [. 902represents the open collating symbol. 903 904@item .] 905represents the close collating symbol. 906 907@item [= 908represents the open equivalence class. 909 910@item =] 911represents the close equivalence class. 912 913@item [: 914represents the open character class followed by a valid character class name. 915 916@item :] 917represents the close character class followed by a valid character class name. 918 919@item - 920represents the range if it's not first or last in a list or the ending point 921of a range. 922 923@item ^ 924represents the characters not in the list. If you want to make the @samp{^} 925character a list item, place it anywhere but first. 926 927@end table 928 929@section Backslash Character 930@cindex backslash 931 932The @samp{\} when followed by certain ordinary characters take a special 933meaning : 934 935@table @samp 936 937@item @samp{\b} 938Match the empty string at the edge of a word. 939 940@item @samp{\B} 941Match the empty string provided it's not at the edge of a word. 942 943@item @samp{\<} 944Match the empty string at the beginning of word. 945 946@item @samp{\>} 947Match the empty string at the end of word. 948 949@item @samp{\w} 950Match word constituent, it is a synonym for @samp{[[:alnum:]]}. 951 952@item @samp{\W} 953Match non word constituent, it is a synonym for @samp{[^[:alnum:]]}. 954 955@end table 956 957For example , @samp{\brat\b} matches the separate word @samp{rat}, 958@samp{c\Brat\Be} matches @samp{crate}, but @samp{dirty \Brat} doesn't 959match @samp{dirty rat}. 960 961@section Anchoring 962@cindex anchoring 963 964The caret @samp{^} and the dollar sign @samp{$} are metacharacters that 965respectively match the empty string at the beginning and end of a line. 966 967@section Back-reference 968@cindex back-reference 969 970The back-reference @samp{\@var{n}}, where @var{n} is a single digit, matches 971the substring previously matched by the @var{n}th parenthesized subexpression 972of the regular expression. For example, @samp{(a)\1} matches @samp{aa}. 973When use with alternation if the group does not participate in the match, then 974the back-reference makes the whole match fail. For example, @samp{a(.)|b\1} 975will not match @samp{ba}. When multiple regular expressions are given with 976@samp{-e} or from a file @samp{-f file}, the back-referecences are local to 977each expression. 978 979@section Basic vs Extended 980@cindex basic regular expressions 981 982In basic regular expressions the metacharacters @samp{?}, @samp{+}, 983@samp{@{}, @samp{|}, @samp{(}, and @samp{)} lose their special meaning; 984instead use the backslashed versions @samp{\?}, @samp{\+}, @samp{\@{}, 985@samp{\|}, @samp{\(}, and @samp{\)}. 986 987@cindex interval specifications 988Traditional @command{egrep} did not support the @samp{@{} metacharacter, 989and some @command{egrep} implementations support @samp{\@{} instead, so 990portable scripts should avoid @samp{@{} in @samp{egrep} patterns and 991should use @samp{[@{]} to match a literal @samp{@{}. 992 993@sc{gnu} @command{egrep} attempts to support traditional usage by 994assuming that @samp{@{} is not special if it would be the start of an 995invalid interval specification. For example, the shell command 996@samp{egrep '@{1'} searches for the two-character string @samp{@{1} 997instead of reporting a syntax error in the regular expression. 998@sc{posix.2} allows this behavior as an extension, but portable scripts 999should avoid it. 1000 1001@node Usage 1002@chapter Usage 1003 1004@cindex Usage, examples 1005Here is an example shell command that invokes @sc{gnu} @command{grep}: 1006 1007@example 1008grep -i 'hello.*world' menu.h main.c 1009@end example 1010 1011@noindent 1012This lists all lines in the files @file{menu.h} and @file{main.c} that 1013contain the string @samp{hello} followed by the string @samp{world}; 1014this is because @samp{.*} matches zero or more characters within a line. 1015@xref{Regular Expressions}. The @samp{-i} option causes @command{grep} 1016to ignore case, causing it to match the line @samp{Hello, world!}, which 1017it would not otherwise match. @xref{Invoking}, for more details about 1018how to invoke @command{grep}. 1019 1020@cindex Using @command{grep}, Q&A 1021@cindex FAQ about @command{grep} usage 1022Here are some common questions and answers about @command{grep} usage. 1023 1024@enumerate 1025 1026@item 1027How can I list just the names of matching files? 1028 1029@example 1030grep -l 'main' *.c 1031@end example 1032 1033@noindent 1034lists the names of all C files in the current directory whose contents 1035mention @samp{main}. 1036 1037@item 1038How do I search directories recursively? 1039 1040@example 1041grep -r 'hello' /home/gigi 1042@end example 1043 1044@noindent 1045searches for @samp{hello} in all files under the directory 1046@file{/home/gigi}. For more control of which files are searched, use 1047@command{find}, @command{grep} and @command{xargs}. For example, 1048the following command searches only C files: 1049 1050@smallexample 1051find /home/gigi -name '*.c' -print | xargs grep 'hello' /dev/null 1052@end smallexample 1053 1054This differs from the command: 1055 1056@example 1057grep -r 'hello' *.c 1058@end example 1059 1060which merely looks for @samp{hello} in all files in the current 1061directory whose names end in @samp{.c}. Here the @option{-r} is 1062probably unnecessary, as recursion occurs only in the unlikely event 1063that one of @samp{.c} files is a directory. 1064 1065@item 1066What if a pattern has a leading @samp{-}? 1067 1068@example 1069grep -e '--cut here--' * 1070@end example 1071 1072@noindent 1073searches for all lines matching @samp{--cut here--}. Without @samp{-e}, 1074@command{grep} would attempt to parse @samp{--cut here--} as a list of 1075options. 1076 1077@item 1078Suppose I want to search for a whole word, not a part of a word? 1079 1080@example 1081grep -w 'hello' * 1082@end example 1083 1084@noindent 1085searches only for instances of @samp{hello} that are entire words; it 1086does not match @samp{Othello}. For more control, use @samp{\<} and 1087@samp{\>} to match the start and end of words. For example: 1088 1089@example 1090grep 'hello\>' * 1091@end example 1092 1093@noindent 1094searches only for words ending in @samp{hello}, so it matches the word 1095@samp{Othello}. 1096 1097@item 1098How do I output context around the matching lines? 1099 1100@example 1101grep -C 2 'hello' * 1102@end example 1103 1104@noindent 1105prints two lines of context around each matching line. 1106 1107@item 1108How do I force grep to print the name of the file? 1109 1110Append @file{/dev/null}: 1111 1112@example 1113grep 'eli' /etc/passwd /dev/null 1114@end example 1115 1116gets you: 1117 1118@smallexample 1119/etc/passwd:eli:DNGUTF58.IMe.:98:11:Eli Smith:/home/do/eli:/bin/bash 1120@end smallexample 1121 1122@item 1123Why do people use strange regular expressions on @command{ps} output? 1124 1125@example 1126ps -ef | grep '[c]ron' 1127@end example 1128 1129If the pattern had been written without the square brackets, it would 1130have matched not only the @command{ps} output line for @command{cron}, 1131but also the @command{ps} output line for @command{grep}. 1132Note that some platforms @command{ps} limit the ouput to the width 1133of the screen, grep does not have any limit on the length of a line 1134except the available memory. 1135 1136@item 1137Why does @command{grep} report ``Binary file matches''? 1138 1139If @command{grep} listed all matching ``lines'' from a binary file, it 1140would probably generate output that is not useful, and it might even 1141muck up your display. So @sc{gnu} @command{grep} suppresses output from 1142files that appear to be binary files. To force @sc{gnu} @command{grep} 1143to output lines even from files that appear to be binary, use the 1144@samp{-a} or @samp{--binary-files=text} option. To eliminate the 1145``Binary file matches'' messages, use the @samp{-I} or 1146@samp{--binary-files=without-match} option. 1147 1148@item 1149Why doesn't @samp{grep -lv} print nonmatching file names? 1150 1151@samp{grep -lv} lists the names of all files containing one or more 1152lines that do not match. To list the names of all files that contain no 1153matching lines, use the @samp{-L} or @samp{--files-without-match} 1154option. 1155 1156@item 1157I can do @sc{or} with @samp{|}, but what about @sc{and}? 1158 1159@example 1160grep 'paul' /etc/motd | grep 'franc,ois' 1161@end example 1162 1163@noindent 1164finds all lines that contain both @samp{paul} and @samp{franc,ois}. 1165 1166@item 1167How can I search in both standard input and in files? 1168 1169Use the special file name @samp{-}: 1170 1171@example 1172cat /etc/passwd | grep 'alain' - /etc/motd 1173@end example 1174 1175@item 1176@cindex palindromes 1177How to express palindromes in a regular expression? 1178 1179It can be done by using the back referecences, for example a palindrome 1180of 4 chararcters can be written in BRE. 1181 1182@example 1183grep -w -e '\(.\)\(.\).\2\1' file 1184@end example 1185 1186It matches the word "radar" or "civic". 1187 1188Guglielmo Bondioni proposed a single RE that finds all the palindromes up to 19 1189characters long. 1190 1191@example 1192egrep -e '^(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?).?\9\8\7\6\5\4\3\2\1$' file 1193@end example 1194 1195Note this is done by using GNU ERE extensions, it might not be portable on 1196other greps. 1197 1198@item 1199Why are my expressions whith the vertical bar fail? 1200 1201@example 1202/bin/echo "ba" | egrep '(a)\1|(b)\1' 1203@end example 1204 1205The first alternate branch fails then the first group was not in the match 1206this will make the second alternate branch fails. For example, "aaba" will 1207match, the first group participate in the match and can be reuse in the 1208second branch. 1209 1210@item 1211What do @command{grep, fgrep, egrep} stand for ? 1212 1213grep comes from the way line editing was done on Unix. For example, 1214@command{ed} uses this syntax to print a list of matching lines on the screen. 1215 1216@example 1217global/regular expression/print 1218g/re/p 1219@end example 1220 1221@command{fgrep} stands for Fixed @command{grep}, @command{egrep} Extended 1222@command{grep}. 1223 1224@end enumerate 1225 1226@node Reporting Bugs, Copying, Usage, Top 1227@chapter Reporting bugs 1228 1229@cindex Bugs, reporting 1230Email bug reports to @email{bug-gnu-utils@@gnu.org}. 1231Be sure to include the word ``grep'' somewhere in the ``Subject:'' field. 1232 1233Large repetition counts in the @samp{@{n,m@}} construct may cause 1234@command{grep} to use lots of memory. In addition, certain other 1235obscure regular expressions require exponential time and 1236space, and may cause grep to run out of memory. 1237Back-references are very slow, and may require exponential time. 1238 1239@node Copying, GNU General Public License, Reporting Bugs, Top 1240@chapter Copying 1241@cindex Copying 1242GNU grep is licensed under the GNU GPL, which makes it @dfn{free 1243software}. 1244 1245Please note that ``free'' in ``free software'' refers to liberty, not 1246price. As some GNU project advocates like to point out, think of ``free 1247speech'' rather than ``free beer''. The exact and legally binding 1248distribution terms are spelled out below; in short, you have the right 1249(freedom) to run and change grep and distribute it to other people, and 1250even---if you want---charge money for doing either. The important 1251restriction is that you have to grant your recipients the same rights 1252and impose the same restrictions. 1253 1254This method of licensing software is also known as @dfn{open source} 1255because, among other things, it makes sure that all recipients will 1256receive the source code along with the program, and be able to improve 1257it. The GNU project prefers the term ``free software'' for reasons 1258outlined at 1259@url{http://www.gnu.org/philosophy/free-software-for-freedom.html}. 1260 1261The exact license terms are defined by this paragraph and the GNU 1262General Public License it refers to: 1263 1264@quotation 1265GNU grep is free software; you can redistribute it and/or modify it 1266under the terms of the GNU General Public License as published by the 1267Free Software Foundation; either version 2 of the License, or (at your 1268option) any later version. 1269 1270GNU grep is distributed in the hope that it will be useful, but WITHOUT 1271ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 1272FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 1273for more details. 1274 1275A copy of the GNU General Public License is included as part of this 1276manual; if you did not receive it, write to the Free Software 1277Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 1278@end quotation 1279 1280In addition to this, this manual is free in the same sense: 1281 1282@quotation 1283Permission is granted to copy, distribute and/or modify this document 1284under the terms of the GNU Free Documentation License, Version 1.1 or 1285any later version published by the Free Software Foundation; with the 1286Invariant Sections being ``GNU General Public License'' and ``GNU Free 1287Documentation License'', with no Front-Cover Texts, and with no 1288Back-Cover Texts. A copy of the license is included in the section 1289entitled ``GNU Free Documentation License''. 1290@end quotation 1291 1292@c #### Maybe we should wrap these licenses in ifinfo? Stallman says 1293@c that the GFDL needs to be present in the manual, and to me it would 1294@c suck to include the license for the manual and not the license for 1295@c the program. 1296 1297The full texts of the GNU General Public License and of the GNU Free 1298Documentation License are available below. 1299 1300@menu 1301* GNU General Public License:: GNU GPL 1302* GNU Free Documentation License:: GNU FDL 1303@end menu 1304 1305@node GNU General Public License, GNU Free Documentation License, Copying, Copying 1306@section GNU General Public License 1307@center Version 2, June 1991 1308@cindex GPL, GNU General Public License 1309 1310@display 1311Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc. 1312675 Mass Ave, Cambridge, MA 02139, USA 1313 1314Everyone is permitted to copy and distribute verbatim copies 1315of this license document, but changing it is not allowed. 1316@end display 1317 1318@unnumberedsec Preamble 1319 1320 The licenses for most software are designed to take away your 1321freedom to share and change it. By contrast, the GNU General Public 1322License is intended to guarantee your freedom to share and change free 1323software---to make sure the software is free for all its users. This 1324General Public License applies to most of the Free Software 1325Foundation's software and to any other program whose authors commit to 1326using it. (Some other Free Software Foundation software is covered by 1327the GNU Library General Public License instead.) You can apply it to 1328your programs, too. 1329 1330 When we speak of free software, we are referring to freedom, not 1331price. 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You may not impose any further 1524restrictions on the recipients' exercise of the rights granted herein. 1525You are not responsible for enforcing compliance by third parties to 1526this License. 1527 1528@item 1529If, as a consequence of a court judgment or allegation of patent 1530infringement or for any other reason (not limited to patent issues), 1531conditions are imposed on you (whether by court order, agreement or 1532otherwise) that contradict the conditions of this License, they do not 1533excuse you from the conditions of this License. If you cannot 1534distribute so as to satisfy simultaneously your obligations under this 1535License and any other pertinent obligations, then as a consequence you 1536may not distribute the Program at all. For example, if a patent 1537license would not permit royalty-free redistribution of the Program by 1538all those who receive copies directly or indirectly through you, then 1539the only way you could satisfy both it and this License would be to 1540refrain entirely from distribution of the Program. 1541 1542If any portion of this section is held invalid or unenforceable under 1543any particular circumstance, the balance of the section is intended to 1544apply and the section as a whole is intended to apply in other 1545circumstances. 1546 1547It is not the purpose of this section to induce you to infringe any 1548patents or other property right claims or to contest validity of any 1549such claims; this section has the sole purpose of protecting the 1550integrity of the free software distribution system, which is 1551implemented by public license practices. Many people have made 1552generous contributions to the wide range of software distributed 1553through that system in reliance on consistent application of that 1554system; it is up to the author/donor to decide if he or she is willing 1555to distribute software through any other system and a licensee cannot 1556impose that choice. 1557 1558This section is intended to make thoroughly clear what is believed to 1559be a consequence of the rest of this License. 1560 1561@item 1562If the distribution and/or use of the Program is restricted in 1563certain countries either by patents or by copyrighted interfaces, the 1564original copyright holder who places the Program under this License 1565may add an explicit geographical distribution limitation excluding 1566those countries, so that distribution is permitted only in or among 1567countries not thus excluded. In such case, this License incorporates 1568the limitation as if written in the body of this License. 1569 1570@item 1571The Free Software Foundation may publish revised and/or new versions 1572of the General Public License from time to time. Such new versions will 1573be similar in spirit to the present version, but may differ in detail to 1574address new problems or concerns. 1575 1576Each version is given a distinguishing version number. If the Program 1577specifies a version number of this License which applies to it and ``any 1578later version'', you have the option of following the terms and conditions 1579either of that version or of any later version published by the Free 1580Software Foundation. If the Program does not specify a version number of 1581this License, you may choose any version ever published by the Free Software 1582Foundation. 1583 1584@item 1585If you wish to incorporate parts of the Program into other free 1586programs whose distribution conditions are different, write to the author 1587to ask for permission. For software which is copyrighted by the Free 1588Software Foundation, write to the Free Software Foundation; we sometimes 1589make exceptions for this. Our decision will be guided by the two goals 1590of preserving the free status of all derivatives of our free software and 1591of promoting the sharing and reuse of software generally. 1592 1593@iftex 1594@heading NO WARRANTY 1595@end iftex 1596@ifinfo 1597@center NO WARRANTY 1598@end ifinfo 1599@cindex no warranty 1600 1601@item 1602BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY 1603FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN 1604OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES 1605PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED 1606OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 1607MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS 1608TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE 1609PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, 1610REPAIR OR CORRECTION. 1611 1612@item 1613IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 1614WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR 1615REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, 1616INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING 1617OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED 1618TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY 1619YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER 1620PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE 1621POSSIBILITY OF SUCH DAMAGES. 1622@end enumerate 1623 1624@iftex 1625@heading END OF TERMS AND CONDITIONS 1626@end iftex 1627@ifinfo 1628@center END OF TERMS AND CONDITIONS 1629@end ifinfo 1630 1631@page 1632@unnumberedsec How to Apply These Terms to Your New Programs 1633 1634 If you develop a new program, and you want it to be of the greatest 1635possible use to the public, the best way to achieve this is to make it 1636free software which everyone can redistribute and change under these terms. 1637 1638 To do so, attach the following notices to the program. It is safest 1639to attach them to the start of each source file to most effectively 1640convey the exclusion of warranty; and each file should have at least 1641the ``copyright'' line and a pointer to where the full notice is found. 1642 1643@smallexample 1644@var{one line to give the program's name and an idea of what it does.} 1645Copyright (C) 19@var{yy} @var{name of author} 1646 1647This program is free software; you can redistribute it and/or 1648modify it under the terms of the GNU General Public License 1649as published by the Free Software Foundation; either version 2 1650of the License, or (at your option) any later version. 1651 1652This program is distributed in the hope that it will be useful, 1653but WITHOUT ANY WARRANTY; without even the implied warranty of 1654MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 1655GNU General Public License for more details. 1656 1657You should have received a copy of the GNU General Public License 1658along with this program; if not, write to the Free Software 1659Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 1660@end smallexample 1661 1662Also add information on how to contact you by electronic and paper mail. 1663 1664If the program is interactive, make it output a short notice like this 1665when it starts in an interactive mode: 1666 1667@smallexample 1668Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author} 1669Gnomovision comes with ABSOLUTELY NO WARRANTY; for details 1670type `show w'. This is free software, and you are welcome 1671to redistribute it under certain conditions; type `show c' 1672for details. 1673@end smallexample 1674 1675The hypothetical commands @samp{show w} and @samp{show c} should show 1676the appropriate parts of the General Public License. Of course, the 1677commands you use may be called something other than @samp{show w} and 1678@samp{show c}; they could even be mouse-clicks or menu items---whatever 1679suits your program. 1680 1681You should also get your employer (if you work as a programmer) or your 1682school, if any, to sign a ``copyright disclaimer'' for the program, if 1683necessary. Here is a sample; alter the names: 1684 1685@smallexample 1686@group 1687Yoyodyne, Inc., hereby disclaims all copyright 1688interest in the program `Gnomovision' 1689(which makes passes at compilers) written 1690by James Hacker. 1691 1692@var{signature of Ty Coon}, 1 April 1989 1693Ty Coon, President of Vice 1694@end group 1695@end smallexample 1696 1697This General Public License does not permit incorporating your program into 1698proprietary programs. If your program is a subroutine library, you may 1699consider it more useful to permit linking proprietary applications with the 1700library. If this is what you want to do, use the GNU Library General 1701Public License instead of this License. 1702 1703@node GNU Free Documentation License, Concept Index, GNU General Public License, Copying 1704@section GNU Free Documentation License 1705@center Version 1.1, March 2000 1706@cindex FDL, GNU Free Documentation License 1707 1708@display 1709Copyright (C) 2000 Free Software Foundation, Inc. 171059 Temple Place, Suite 330, Boston, MA 02111-1307 USA 1711 1712Everyone is permitted to copy and distribute verbatim copies 1713of this license document, but changing it is not allowed. 1714@end display 1715@sp 1 1716@enumerate 0 1717@item 1718PREAMBLE 1719 1720The purpose of this License is to make a manual, textbook, or other 1721written document ``free'' in the sense of freedom: to assure everyone 1722the effective freedom to copy and redistribute it, with or without 1723modifying it, either commercially or noncommercially. Secondarily, 1724this License preserves for the author and publisher a way to get 1725credit for their work, while not being considered responsible for 1726modifications made by others. 1727 1728This License is a kind of ``copyleft'', which means that derivative 1729works of the document must themselves be free in the same sense. It 1730complements the GNU General Public License, which is a copyleft 1731license designed for free software. 1732 1733We have designed this License in order to use it for manuals for free 1734software, because free software needs free documentation: a free 1735program should come with manuals providing the same freedoms that the 1736software does. But this License is not limited to software manuals; 1737it can be used for any textual work, regardless of subject matter or 1738whether it is published as a printed book. We recommend this License 1739principally for works whose purpose is instruction or reference. 1740 1741@sp 1 1742@item 1743APPLICABILITY AND DEFINITIONS 1744 1745This License applies to any manual or other work that contains a 1746notice placed by the copyright holder saying it can be distributed 1747under the terms of this License. The ``Document'', below, refers to any 1748such manual or work. Any member of the public is a licensee, and is 1749addressed as ``you''. 1750 1751A ``Modified Version'' of the Document means any work containing the 1752Document or a portion of it, either copied verbatim, or with 1753modifications and/or translated into another language. 1754 1755A ``Secondary Section'' is a named appendix or a front-matter section of 1756the Document that deals exclusively with the relationship of the 1757publishers or authors of the Document to the Document's overall subject 1758(or to related matters) and contains nothing that could fall directly 1759within that overall subject. (For example, if the Document is in part a 1760textbook of mathematics, a Secondary Section may not explain any 1761mathematics.) The relationship could be a matter of historical 1762connection with the subject or with related matters, or of legal, 1763commercial, philosophical, ethical or political position regarding 1764them. 1765 1766The ``Invariant Sections'' are certain Secondary Sections whose titles 1767are designated, as being those of Invariant Sections, in the notice 1768that says that the Document is released under this License. 1769 1770The ``Cover Texts'' are certain short passages of text that are listed, 1771as Front-Cover Texts or Back-Cover Texts, in the notice that says that 1772the Document is released under this License. 1773 1774A ``Transparent'' copy of the Document means a machine-readable copy, 1775represented in a format whose specification is available to the 1776general public, whose contents can be viewed and edited directly and 1777straightforwardly with generic text editors or (for images composed of 1778pixels) generic paint programs or (for drawings) some widely available 1779drawing editor, and that is suitable for input to text formatters or 1780for automatic translation to a variety of formats suitable for input 1781to text formatters. A copy made in an otherwise Transparent file 1782format whose markup has been designed to thwart or discourage 1783subsequent modification by readers is not Transparent. A copy that is 1784not ``Transparent'' is called ``Opaque''. 1785 1786Examples of suitable formats for Transparent copies include plain 1787ASCII without markup, Texinfo input format, LaTeX input format, SGML 1788or XML using a publicly available DTD, and standard-conforming simple 1789HTML designed for human modification. Opaque formats include 1790PostScript, PDF, proprietary formats that can be read and edited only 1791by proprietary word processors, SGML or XML for which the DTD and/or 1792processing tools are not generally available, and the 1793machine-generated HTML produced by some word processors for output 1794purposes only. 1795 1796The ``Title Page'' means, for a printed book, the title page itself, 1797plus such following pages as are needed to hold, legibly, the material 1798this License requires to appear in the title page. For works in 1799formats which do not have any title page as such, ``Title Page'' means 1800the text near the most prominent appearance of the work's title, 1801preceding the beginning of the body of the text. 1802@sp 1 1803@item 1804VERBATIM COPYING 1805 1806You may copy and distribute the Document in any medium, either 1807commercially or noncommercially, provided that this License, the 1808copyright notices, and the license notice saying this License applies 1809to the Document are reproduced in all copies, and that you add no other 1810conditions whatsoever to those of this License. You may not use 1811technical measures to obstruct or control the reading or further 1812copying of the copies you make or distribute. However, you may accept 1813compensation in exchange for copies. If you distribute a large enough 1814number of copies you must also follow the conditions in section 3. 1815 1816You may also lend copies, under the same conditions stated above, and 1817you may publicly display copies. 1818@sp 1 1819@item 1820COPYING IN QUANTITY 1821 1822If you publish printed copies of the Document numbering more than 100, 1823and the Document's license notice requires Cover Texts, you must enclose 1824the copies in covers that carry, clearly and legibly, all these Cover 1825Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on 1826the back cover. Both covers must also clearly and legibly identify 1827you as the publisher of these copies. The front cover must present 1828the full title with all words of the title equally prominent and 1829visible. You may add other material on the covers in addition. 1830Copying with changes limited to the covers, as long as they preserve 1831the title of the Document and satisfy these conditions, can be treated 1832as verbatim copying in other respects. 1833 1834If the required texts for either cover are too voluminous to fit 1835legibly, you should put the first ones listed (as many as fit 1836reasonably) on the actual cover, and continue the rest onto adjacent 1837pages. 1838 1839If you publish or distribute Opaque copies of the Document numbering 1840more than 100, you must either include a machine-readable Transparent 1841copy along with each Opaque copy, or state in or with each Opaque copy 1842a publicly-accessible computer-network location containing a complete 1843Transparent copy of the Document, free of added material, which the 1844general network-using public has access to download anonymously at no 1845charge using public-standard network protocols. If you use the latter 1846option, you must take reasonably prudent steps, when you begin 1847distribution of Opaque copies in quantity, to ensure that this 1848Transparent copy will remain thus accessible at the stated location 1849until at least one year after the last time you distribute an Opaque 1850copy (directly or through your agents or retailers) of that edition to 1851the public. 1852 1853It is requested, but not required, that you contact the authors of the 1854Document well before redistributing any large number of copies, to give 1855them a chance to provide you with an updated version of the Document. 1856@sp 1 1857@item 1858MODIFICATIONS 1859 1860You may copy and distribute a Modified Version of the Document under 1861the conditions of sections 2 and 3 above, provided that you release 1862the Modified Version under precisely this License, with the Modified 1863Version filling the role of the Document, thus licensing distribution 1864and modification of the Modified Version to whoever possesses a copy 1865of it. In addition, you must do these things in the Modified Version: 1866 1867A. Use in the Title Page (and on the covers, if any) a title distinct 1868 from that of the Document, and from those of previous versions 1869 (which should, if there were any, be listed in the History section 1870 of the Document). You may use the same title as a previous version 1871 if the original publisher of that version gives permission.@* 1872B. List on the Title Page, as authors, one or more persons or entities 1873 responsible for authorship of the modifications in the Modified 1874 Version, together with at least five of the principal authors of the 1875 Document (all of its principal authors, if it has less than five).@* 1876C. State on the Title page the name of the publisher of the 1877 Modified Version, as the publisher.@* 1878D. Preserve all the copyright notices of the Document.@* 1879E. Add an appropriate copyright notice for your modifications 1880 adjacent to the other copyright notices.@* 1881F. Include, immediately after the copyright notices, a license notice 1882 giving the public permission to use the Modified Version under the 1883 terms of this License, in the form shown in the Addendum below.@* 1884G. Preserve in that license notice the full lists of Invariant Sections 1885 and required Cover Texts given in the Document's license notice.@* 1886H. Include an unaltered copy of this License.@* 1887I. Preserve the section entitled ``History'', and its title, and add to 1888 it an item stating at least the title, year, new authors, and 1889 publisher of the Modified Version as given on the Title Page. If 1890 there is no section entitled ``History'' in the Document, create one 1891 stating the title, year, authors, and publisher of the Document as 1892 given on its Title Page, then add an item describing the Modified 1893 Version as stated in the previous sentence.@* 1894J. Preserve the network location, if any, given in the Document for 1895 public access to a Transparent copy of the Document, and likewise 1896 the network locations given in the Document for previous versions 1897 it was based on. These may be placed in the ``History'' section. 1898 You may omit a network location for a work that was published at 1899 least four years before the Document itself, or if the original 1900 publisher of the version it refers to gives permission.@* 1901K. In any section entitled ``Acknowledgements'' or ``Dedications'', 1902 preserve the section's title, and preserve in the section all the 1903 substance and tone of each of the contributor acknowledgements 1904 and/or dedications given therein.@* 1905L. Preserve all the Invariant Sections of the Document, 1906 unaltered in their text and in their titles. Section numbers 1907 or the equivalent are not considered part of the section titles.@* 1908M. Delete any section entitled ``Endorsements''. Such a section 1909 may not be included in the Modified Version.@* 1910N. Do not retitle any existing section as ``Endorsements'' 1911 or to conflict in title with any Invariant Section.@* 1912@sp 1 1913If the Modified Version includes new front-matter sections or 1914appendices that qualify as Secondary Sections and contain no material 1915copied from the Document, you may at your option designate some or all 1916of these sections as invariant. To do this, add their titles to the 1917list of Invariant Sections in the Modified Version's license notice. 1918These titles must be distinct from any other section titles. 1919 1920You may add a section entitled ``Endorsements'', provided it contains 1921nothing but endorsements of your Modified Version by various 1922parties--for example, statements of peer review or that the text has 1923been approved by an organization as the authoritative definition of a 1924standard. 1925 1926You may add a passage of up to five words as a Front-Cover Text, and a 1927passage of up to 25 words as a Back-Cover Text, to the end of the list 1928of Cover Texts in the Modified Version. Only one passage of 1929Front-Cover Text and one of Back-Cover Text may be added by (or 1930through arrangements made by) any one entity. If the Document already 1931includes a cover text for the same cover, previously added by you or 1932by arrangement made by the same entity you are acting on behalf of, 1933you may not add another; but you may replace the old one, on explicit 1934permission from the previous publisher that added the old one. 1935 1936The author(s) and publisher(s) of the Document do not by this License 1937give permission to use their names for publicity for or to assert or 1938imply endorsement of any Modified Version. 1939@sp 1 1940@item 1941COMBINING DOCUMENTS 1942 1943You may combine the Document with other documents released under this 1944License, under the terms defined in section 4 above for modified 1945versions, provided that you include in the combination all of the 1946Invariant Sections of all of the original documents, unmodified, and 1947list them all as Invariant Sections of your combined work in its 1948license notice. 1949 1950The combined work need only contain one copy of this License, and 1951multiple identical Invariant Sections may be replaced with a single 1952copy. If there are multiple Invariant Sections with the same name but 1953different contents, make the title of each such section unique by 1954adding at the end of it, in parentheses, the name of the original 1955author or publisher of that section if known, or else a unique number. 1956Make the same adjustment to the section titles in the list of 1957Invariant Sections in the license notice of the combined work. 1958 1959In the combination, you must combine any sections entitled ``History'' 1960in the various original documents, forming one section entitled 1961``History''; likewise combine any sections entitled ``Acknowledgements'', 1962and any sections entitled ``Dedications''. You must delete all sections 1963entitled ``Endorsements.'' 1964@sp 1 1965@item 1966COLLECTIONS OF DOCUMENTS 1967 1968You may make a collection consisting of the Document and other documents 1969released under this License, and replace the individual copies of this 1970License in the various documents with a single copy that is included in 1971the collection, provided that you follow the rules of this License for 1972verbatim copying of each of the documents in all other respects. 1973 1974You may extract a single document from such a collection, and distribute 1975it individually under this License, provided you insert a copy of this 1976License into the extracted document, and follow this License in all 1977other respects regarding verbatim copying of that document. 1978@sp 1 1979@item 1980AGGREGATION WITH INDEPENDENT WORKS 1981 1982A compilation of the Document or its derivatives with other separate 1983and independent documents or works, in or on a volume of a storage or 1984distribution medium, does not as a whole count as a Modified Version 1985of the Document, provided no compilation copyright is claimed for the 1986compilation. Such a compilation is called an ``aggregate'', and this 1987License does not apply to the other self-contained works thus compiled 1988with the Document, on account of their being thus compiled, if they 1989are not themselves derivative works of the Document. 1990 1991If the Cover Text requirement of section 3 is applicable to these 1992copies of the Document, then if the Document is less than one quarter 1993of the entire aggregate, the Document's Cover Texts may be placed on 1994covers that surround only the Document within the aggregate. 1995Otherwise they must appear on covers around the whole aggregate. 1996@sp 1 1997@item 1998TRANSLATION 1999 2000Translation is considered a kind of modification, so you may 2001distribute translations of the Document under the terms of section 4. 2002Replacing Invariant Sections with translations requires special 2003permission from their copyright holders, but you may include 2004translations of some or all Invariant Sections in addition to the 2005original versions of these Invariant Sections. You may include a 2006translation of this License provided that you also include the 2007original English version of this License. In case of a disagreement 2008between the translation and the original English version of this 2009License, the original English version will prevail. 2010@sp 1 2011@item 2012TERMINATION 2013 2014You may not copy, modify, sublicense, or distribute the Document except 2015as expressly provided for under this License. Any other attempt to 2016copy, modify, sublicense or distribute the Document is void, and will 2017automatically terminate your rights under this License. However, 2018parties who have received copies, or rights, from you under this 2019License will not have their licenses terminated so long as such 2020parties remain in full compliance. 2021@sp 1 2022@item 2023FUTURE REVISIONS OF THIS LICENSE 2024 2025The Free Software Foundation may publish new, revised versions 2026of the GNU Free Documentation License from time to time. Such new 2027versions will be similar in spirit to the present version, but may 2028differ in detail to address new problems or concerns. See 2029http://www.gnu.org/copyleft/. 2030 2031Each version of the License is given a distinguishing version number. 2032If the Document specifies that a particular numbered version of this 2033License ``or any later version'' applies to it, you have the option of 2034following the terms and conditions either of that specified version or 2035of any later version that has been published (not as a draft) by the 2036Free Software Foundation. If the Document does not specify a version 2037number of this License, you may choose any version ever published (not 2038as a draft) by the Free Software Foundation. 2039 2040@end enumerate 2041 2042@unnumberedsec ADDENDUM: How to use this License for your documents 2043 2044To use this License in a document you have written, include a copy of 2045the License in the document and put the following copyright and 2046license notices just after the title page: 2047 2048@smallexample 2049@group 2050 2051 Copyright (C) @var{year} @var{your name}. 2052 Permission is granted to copy, distribute and/or modify this document 2053 under the terms of the GNU Free Documentation License, Version 1.1 2054 or any later version published by the Free Software Foundation; 2055 with the Invariant Sections being @var{list their titles}, with the 2056 Front-Cover Texts being @var{list}, and with the Back-Cover Texts being @var{list}. 2057 A copy of the license is included in the section entitled ``GNU 2058 Free Documentation License''. 2059@end group 2060@end smallexample 2061If you have no Invariant Sections, write ``with no Invariant Sections'' 2062instead of saying which ones are invariant. If you have no 2063Front-Cover Texts, write ``no Front-Cover Texts'' instead of 2064``Front-Cover Texts being @var{list}''; likewise for Back-Cover Texts. 2065 2066If your document contains nontrivial examples of program code, we 2067recommend releasing these examples in parallel under your choice of 2068free software license, such as the GNU General Public License, 2069to permit their use in free software. 2070 2071@page 2072@node Concept Index, Index, GNU Free Documentation License, Top 2073@unnumbered Concept Index 2074 2075This is a general index of all issues discussed in this manual, with the 2076exception of the @command{grep} commands and command-line options. 2077 2078@printindex cp 2079 2080@page 2081@node Index,, Concept Index, Top 2082@unnumbered Index 2083 2084This is an alphabetical list of all @command{grep} commands, command-line 2085options, and environment variables. 2086 2087@printindex fn 2088 2089@contents 2090@bye 2091