@(#) $OpenBSD: m4.1,v 1.56 2009/10/14 17:19:47 sthen Exp $
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$FreeBSD: head/usr.bin/m4/m4.1 228063 2011-11-28 13:32:39Z bapt $
.Dd October 14, 2009 .Dt M4 1 .Os .Sh NAME .Nm m4 .Nd macro language processor .Sh SYNOPSIS .Nm m4 .Op Fl gPs .Oo .Sm off .Fl D Ar name Op No = Ar value .Sm on .Oc .Op Fl d Ar flags .Op Fl I Ar dirname .Op Fl o Ar filename k -words .Op Fl t Ar macro .Op Fl U Ns Ar name .Op Ar .Ek .Sh DESCRIPTION The .Nm m4 utility is a macro processor that can be used as a front end to any language (e.g., C, ratfor, fortran, lex, and yacc). If no input files are given, .Nm m4 reads from the standard input, otherwise files specified on the command line are processed in the given order. Input files can be regular files, files in the m4 include paths, or a single dash
q Sq - , denoting standard input. .Nm m4 writes the processed text to the standard output, unless told otherwise.
p Macro calls have the form name(argument1[, argument2, ..., argumentN]).
p There cannot be any space following the macro name and the open parenthesis .Sq ( . If the macro name is not followed by an open parenthesis it is processed with no arguments.
p Macro names consist of a leading alphabetic or underscore possibly followed by alphanumeric or underscore characters, e.g., valid macro names match the pattern .Dq [a-zA-Z_][a-zA-Z0-9_]* .
p In arguments to macros, leading unquoted space, tab, and newline
q Sq \en characters are ignored. To quote strings, use left and right single quotes
o e.g., \& .Sq " this is a string with a leading space"
c . You can change the quote characters with the c changequote built-in macro.
p Most built-ins don't make any sense without arguments, and hence are not recognized as special when not followed by an open parenthesis.
p The options are as follows: l -tag -width Ds t Fl D Ns Ar name Ns Op Pf = Ns Ar value Define the symbol .Ar name to have some value (or .Dv NULL ) . t Fl d Ar "flags" Set trace flags. .Ar flags may hold the following: l -tag -width Ds t Ar a print macro arguments. t Ar c print macro expansion over several lines. t Ar e print result of macro expansion. t Ar f print filename location. t Ar l print line number. t Ar q quote arguments and expansion with the current quotes. t Ar t start with all macros traced. t Ar x number macro expansions. t Ar V turn on all options. .El
p By default, trace is set to .Qq eq . t Fl g Activate GNU-m4 compatibility mode. In this mode, translit handles simple character ranges (e.g., a-z), regular expressions mimic emacs behavior, multiple m4wrap calls are handled as a stack, the number of diversions is unlimited, empty names for macro definitions are allowed, and eval understands .Sq 0rbase:value numbers. t Fl I Ar "dirname" Add directory .Ar dirname to the include path. t Fl o Ar filename Send trace output to .Ar filename . t Fl P Prefix all built-in macros with .Sq m4_ . For example, instead of writing c define , use c m4_define . t Fl s Output line synchronization directives, suitable for .Xr cpp 1 . t Fl t Ar macro Turn tracing on for .Ar macro . t Fl "U" Ns Ar "name" Undefine the symbol .Ar name . .El .Sh SYNTAX .Nm m4 provides the following built-in macros. They may be redefined, losing their original meaning. Return values are null unless otherwise stated. l -tag -width changequote t Fn builtin name Calls a built-in by its .Fa name , overriding possible redefinitions. t Fn changecom startcomment endcomment Changes the start comment and end comment sequences. Comment sequences may be up to five characters long. The default values are the hash sign and the newline character. d -literal -offset indent # This is a comment .Ed
p With no arguments, comments are turned off. With one single argument, the end comment sequence is set to the newline character. t Fn changequote beginquote endquote Defines the open quote and close quote sequences. Quote sequences may be up to five characters long. The default values are the backquote character and the quote character. d -literal -offset indent `Here is a quoted string' .Ed
p With no arguments, the default quotes are restored. With one single argument, the close quote sequence is set to the newline character. t Fn decr arg Decrements the argument .Fa arg by 1. The argument .Fa arg must be a valid numeric string. t Fn define name value Define a new macro named by the first argument .Fa name to have the value of the second argument .Fa value . Each occurrence of .Sq $n (where .Ar n is 0 through 9) is replaced by the .Ar n Ns 'th argument. .Sq $0 is the name of the calling macro. Undefined arguments are replaced by a null string. .Sq $# is replaced by the number of arguments; .Sq $* is replaced by all arguments comma separated; .Sq $@ is the same as .Sq $* but all arguments are quoted against further expansion. t Fn defn name ... Returns the quoted definition for each argument. This can be used to rename macro definitions (even for built-in macros). t Fn divert num There are 10 output queues (numbered 0-9). At the end of processing .Nm m4 concatenates all the queues in numerical order to produce the final output. Initially the output queue is 0. The divert macro allows you to select a new output queue (an invalid argument passed to divert causes output to be discarded). t Ic divnum Returns the current output queue number. t Ic dnl Discard input characters up to and including the next newline. t Fn dumpdef name ... Prints the names and definitions for the named items, or for everything if no arguments are passed. t Fn errprint msg Prints the first argument on the standard error output stream. t Fn esyscmd cmd Passes its first argument to a shell and returns the shell's standard output. Note that the shell shares its standard input and standard error with .Nm m4 . t Fn eval expr Computes the first argument as an arithmetic expression using 32-bit arithmetic. Operators are the standard C ternary, arithmetic, logical, shift, relational, bitwise, and parentheses operators. You can specify octal, decimal, and hexadecimal numbers as in C. The second argument (if any) specifies the radix for the result and the third argument (if any) specifies the minimum number of digits in the result. t Fn expr expr This is an alias for c eval . t Fn format formatstring arg1 ... Returns .Fa formatstring with escape sequences substituted with .Fa arg1 and following arguments, in a way similar to .Xr printf 3 . This built-in is only available in GNU-m4 compatibility mode, and the only parameters implemented are there for autoconf compatibility: left-padding flag, an optional field width, a maximum field width, *-specified field widths, and the %s and %c data type. t Fn ifdef name yes no If the macro named by the first argument is defined then return the second argument, otherwise the third. If there is no third argument, the value is .Dv NULL . The word .Qq unix is predefined. t Fn ifelse a b yes ... If the first argument .Fa a matches the second argument .Fa b then .Fn ifelse returns the third argument .Fa yes . If the match fails the three arguments are discarded and the next three arguments are used until there is zero or one arguments left, either this last argument or .Dv NULL is returned if no other matches were found. t Fn include name Returns the contents of the file specified in the first argument. If the file is not found as is, look through the include path: first the directories specified with .Fl I on the command line, then the environment variable .Ev M4PATH , as a colon-separated list of directories. Include aborts with an error message if the file cannot be included. t Fn incr arg Increments the argument by 1. The argument must be a valid numeric string. t Fn index string substring Returns the index of the second argument in the first argument (e.g., c index(the quick brown fox jumped, fox) returns 16). If the second argument is not found index returns -1. t Fn indir macro arg1 ... Indirectly calls the macro whose name is passed as the first argument, with the remaining arguments passed as first, ... arguments. t Fn len arg Returns the number of characters in the first argument. Extra arguments are ignored. t Fn m4exit code Immediately exits with the return value specified by the first argument, 0 if none. t Fn m4wrap todo Allows you to define what happens at the final .Dv EOF , usually for cleanup purposes (e.g., c m4wrap("cleanup(tempfile)") causes the macro cleanup to be invoked after all other processing is done).
p Multiple calls to .Fn m4wrap get inserted in sequence at the final .Dv EOF . t Fn maketemp template Invokes .Xr mkstemp 3 on the first argument, and returns the modified string. This can be used to create unique temporary file names. t Fn paste file Includes the contents of the file specified by the first argument without any macro processing. Aborts with an error message if the file cannot be included. t Fn patsubst string regexp replacement Substitutes a regular expression in a string with a replacement string. Usual substitution patterns apply: an ampersand
q Sq & is replaced by the string matching the regular expression. The string .Sq \e# , where .Sq # is a digit, is replaced by the corresponding back-reference. t Fn popdef arg ... Restores the c pushdef Ns ed definition for each argument. t Fn pushdef macro def Takes the same arguments as c define , but it saves the definition on a stack for later retrieval by .Fn popdef . t Fn regexp string regexp replacement Finds a regular expression in a string. If no further arguments are given, it returns the first match position or -1 if no match. If a third argument is provided, it returns the replacement string, with sub-patterns replaced. t Fn shift arg1 ... Returns all but the first argument, the remaining arguments are quoted and pushed back with commas in between. The quoting nullifies the effect of the extra scan that will subsequently be performed. t Fn sinclude file Similar to c include , except it ignores any errors. t Fn spaste file Similar to .Fn paste , except it ignores any errors. t Fn substr string offset length Returns a substring of the first argument starting at the offset specified by the second argument and the length specified by the third argument. If no third argument is present it returns the rest of the string. t Fn syscmd cmd Passes the first argument to the shell. Nothing is returned. t Ic sysval Returns the return value from the last c syscmd . t Fn traceon arg ... Enables tracing of macro expansions for the given arguments, or for all macros if no argument is given. t Fn traceoff arg ... Disables tracing of macro expansions for the given arguments, or for all macros if no argument is given. t Fn translit string mapfrom mapto Transliterate the characters in the first argument from the set given by the second argument to the set given by the third. You cannot use .Xr tr 1 style abbreviations. t Fn undefine name1 ... Removes the definition for the macros specified by its arguments. t Fn undivert arg ... Flushes the named output queues (or all queues if no arguments). t Ic unix A pre-defined macro for testing the OS platform. t Ic __line__ Returns the current file's line number. t Ic __file__ Returns the current file's name. .El .Sh STANDARDS The .Nm utility is compliant with the .St -p1003.1-2008 specification.
p The flags .Op Fl dgIot and the macros c builtin , c esyscmd , c expr , c format , c indir , c paste , c patsubst , c regexp , c spaste , c unix , c __line__ , and c __file__ are extensions to that specification.
p The output format of tracing and of c dumpdef are not specified in any standard, are likely to change and should not be relied upon. The current format of tracing is closely modelled on .Nm gnu-m4 , to allow .Nm autoconf to work.
p The built-ins c pushdef and c popdef handle macro definitions as a stack. However, c define interacts with the stack in an undefined way. In this implementation, c define replaces the top-most definition only. Other implementations may erase all definitions on the stack instead.
p All built-ins do expand without arguments in many other .Nm m4 .
p Many other .Nm have dire size limitations with respect to buffer sizes. .Sh AUTHORS .An -nosplit .An Ozan Yigit Aq oz@sis.yorku.ca and .An Richard A. O'Keefe Aq ok@goanna.cs.rmit.OZ.AU .
p GNU-m4 compatibility extensions by .An Marc Espie Aq espie@cvs.openbsd.org .