| blob | 3b09dfd224281360b92c8a728238bbb88bc1831a |
1 .\" $NetBSD: m4.1,v 1.20 2009/10/26 21:11:28 christos Exp $
2 .\" @(#) $OpenBSD: m4.1,v 1.56 2009/10/14 17:19:47 sthen Exp $
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7 .\" This code is derived from software contributed to Berkeley by
8 .\" Ozan Yigit at York University.
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34 .Dd October 14, 2009
35 .Dt M4 1
36 .Os
37 .Sh NAME
38 .Nm m4
39 .Nd macro language processor
40 .Sh SYNOPSIS
41 .Nm m4
42 .Op Fl gPs
43 .Oo
44 .Sm off
45 .Fl D Ar name Op No = Ar value
46 .Sm on
47 .Oc
48 .Op Fl d Ar flags
49 .Op Fl I Ar dirname
50 .Op Fl o Ar filename
51 .Bk -words
52 .Op Fl t Ar macro
53 .Op Fl U Ns Ar name
54 .Op Ar
55 .Ek
56 .Sh DESCRIPTION
57 The
58 .Nm m4
59 utility is a macro processor that can be used as a front end to any
60 language (e.g., C, ratfor, fortran, lex, and yacc).
61 If no input files are given,
62 .Nm m4
63 reads from the standard input,
64 otherwise files specified on the command line are
65 processed in the given order.
66 Input files can be regular files, files in the m4 include paths, or a
67 single dash
68 .Pq Sq - ,
69 denoting standard input.
70 .Nm m4
71 writes
72 the processed text to the standard output, unless told otherwise.
73 .Pp
74 Macro calls have the form name(argument1[, argument2, ..., argumentN]).
75 .Pp
76 There cannot be any space following the macro name and the open
77 parenthesis
78 .Pq Sq ( .
79 If the macro name is not followed by an open
80 parenthesis it is processed with no arguments.
81 .Pp
82 Macro names consist of a leading alphabetic or underscore
83 possibly followed by alphanumeric or underscore characters, e.g.,
84 valid macro names match the pattern
85 .Dq [a-zA-Z_][a-zA-Z0-9_]* .
86 .Pp
87 In arguments to macros, leading unquoted space, tab, and newline
88 .Pq Sq \en
89 characters are ignored.
90 To quote strings, use left and right single quotes
91 .Po e.g.,\ \&
92 .Sq "\ this is a string with a leading space"
93 .Pc .
94 You can change the quote characters with the
95 .Ic changequote
96 built-in macro.
97 .Pp
98 Most built-ins don't make any sense without arguments, and hence are not
99 recognized as special when not followed by an open parenthesis.
100 .Pp
101 The options are as follows:
102 .Bl -tag -width Ds
103 .It Fl D Ns Ar name Ns Op Pf = Ns Ar value
104 Define the symbol
105 .Ar name
106 to have some value (or
107 .Dv NULL ) .
108 .It Fl d Ar "flags"
109 Set trace flags.
110 .Ar flags
111 may hold the following:
112 .Bl -tag -width Ds
113 .It Ar a
114 print macro arguments.
115 .It Ar c
116 print macro expansion over several lines.
117 .It Ar e
118 print result of macro expansion.
119 .It Ar f
120 print filename location.
121 .It Ar l
122 print line number.
123 .It Ar q
124 quote arguments and expansion with the current quotes.
125 .It Ar t
126 start with all macros traced.
127 .It Ar x
128 number macro expansions.
129 .It Ar V
130 turn on all options.
131 .El
132 .Pp
133 By default, trace is set to
134 .Qq eq .
135 .It Fl g
136 Activate GNU-m4 compatibility mode.
137 In this mode, translit handles simple character
138 ranges (e.g., a-z), regular expressions mimic emacs behavior,
139 multiple m4wrap calls are handled as a stack,
140 the number of diversions is unlimited,
141 empty names for macro definitions are allowed,
142 and eval understands
143 .Sq 0rbase:value
144 numbers.
145 .It Fl I Ar "dirname"
146 Add directory
147 .Ar dirname
148 to the include path.
149 .It Fl o Ar filename
150 Send trace output to
151 .Ar filename .
152 .It Fl P
153 Prefix all built-in macros with
154 .Sq m4_ .
155 For example, instead of writing
156 .Ic define ,
157 use
158 .Ic m4_define .
159 .It Fl s
160 Output line synchronization directives, suitable for
161 .Xr cpp 1 .
162 .It Fl t Ar macro
163 Turn tracing on for
164 .Ar macro .
165 .It Fl "U" Ns Ar "name"
166 Undefine the symbol
167 .Ar name .
168 .El
169 .Sh SYNTAX
170 .Nm m4
171 provides the following built-in macros.
172 They may be redefined, losing their original meaning.
173 Return values are null unless otherwise stated.
174 .Bl -tag -width changequote
175 .It Fn builtin name
176 Calls a built-in by its
177 .Fa name ,
178 overriding possible redefinitions.
179 .It Fn changecom startcomment endcomment
180 Changes the start comment and end comment sequences.
181 Comment sequences may be up to five characters long.
182 The default values are the hash sign
183 and the newline character.
184 .Bd -literal -offset indent
185 # This is a comment
186 .Ed
187 .Pp
188 With no arguments, comments are turned off.
189 With one single argument, the end comment sequence is set
190 to the newline character.
191 .It Fn changequote beginquote endquote
192 Defines the open quote and close quote sequences.
193 Quote sequences may be up to five characters long.
194 The default values are the backquote character and the quote
195 character.
196 .Bd -literal -offset indent
197 `Here is a quoted string'
198 .Ed
199 .Pp
200 With no arguments, the default quotes are restored.
201 With one single argument, the close quote sequence is set
202 to the newline character.
203 .It Fn decr arg
204 Decrements the argument
205 .Fa arg
206 by 1.
207 The argument
208 .Fa arg
209 must be a valid numeric string.
210 .It Fn define name value
211 Define a new macro named by the first argument
212 .Fa name
213 to have the
214 value of the second argument
215 .Fa value .
216 Each occurrence of
217 .Sq $n
218 (where
219 .Ar n
220 is 0 through 9) is replaced by the
221 .Ar n Ns 'th
222 argument.
223 .Sq $0
224 is the name of the calling macro.
225 Undefined arguments are replaced by a null string.
226 .Sq $#
227 is replaced by the number of arguments;
228 .Sq $*
229 is replaced by all arguments comma separated;
230 .Sq $@
231 is the same as
232 .Sq $*
233 but all arguments are quoted against further expansion.
234 .It Fn defn name ...
235 Returns the quoted definition for each argument.
236 This can be used to rename
237 macro definitions (even for built-in macros).
238 .It Fn divert num
239 There are 10 output queues (numbered 0-9).
240 At the end of processing
241 .Nm m4
242 concatenates all the queues in numerical order to produce the
243 final output.
244 Initially the output queue is 0.
245 The divert
246 macro allows you to select a new output queue (an invalid argument
247 passed to divert causes output to be discarded).
248 .It Ic divnum
249 Returns the current output queue number.
250 .It Ic dnl
251 Discard input characters up to and including the next newline.
252 .It Fn dumpdef name ...
253 Prints the names and definitions for the named items, or for everything
254 if no arguments are passed.
255 .It Fn errprint msg
256 Prints the first argument on the standard error output stream.
257 .It Fn esyscmd cmd
258 Passes its first argument to a shell and returns the shell's standard output.
259 Note that the shell shares its standard input and standard error with
260 .Nm m4 .
261 .It Fn eval expr
262 Computes the first argument as an arithmetic expression using 32-bit
263 arithmetic.
264 Operators are the standard C ternary, arithmetic, logical,
265 shift, relational, bitwise, and parentheses operators.
266 You can specify
267 octal, decimal, and hexadecimal numbers as in C.
268 The second argument (if any)
269 specifies the radix for the result and the third argument (if any)
270 specifies the minimum number of digits in the result.
271 .It Fn expr expr
272 This is an alias for
273 .Ic eval .
274 .It Fn format formatstring arg1 ...
275 Returns
276 .Fa formatstring
277 with escape sequences substituted with
278 .Fa arg1
279 and following arguments, in a way similar to
280 .Xr printf 3 .
281 This built-in is only available in GNU-m4 compatibility mode, and the only
282 parameters implemented are there for autoconf compatibility:
283 left-padding flag, an optional field width, a maximum field width,
284 *-specified field widths, and the %s and %c data type.
285 .It Fn ifdef name yes no
286 If the macro named by the first argument is defined then return the second
287 argument, otherwise the third.
288 If there is no third argument, the value is
289 .Dv NULL .
290 The word
291 .Qq unix
292 is predefined.
293 .It Fn ifelse a b yes ...
294 If the first argument
295 .Fa a
296 matches the second argument
297 .Fa b
298 then
299 .Fn ifelse
300 returns
301 the third argument
302 .Fa yes .
303 If the match fails the three arguments are
304 discarded and the next three arguments are used until there is
305 zero or one arguments left, either this last argument or
306 .Dv NULL
307 is returned if no other matches were found.
308 .It Fn include name
309 Returns the contents of the file specified in the first argument.
310 If the file is not found as is, look through the include path:
311 first the directories specified with
312 .Fl I
313 on the command line, then the environment variable
314 .Ev M4PATH ,
315 as a colon-separated list of directories.
316 Include aborts with an error message if the file cannot be included.
317 .It Fn incr arg
318 Increments the argument by 1.
319 The argument must be a valid numeric string.
320 .It Fn index string substring
321 Returns the index of the second argument in the first argument (e.g.,
322 .Ic index(the quick brown fox jumped, fox)
323 returns 16).
324 If the second
325 argument is not found index returns \-1.
326 .It Fn indir macro arg1 ...
327 Indirectly calls the macro whose name is passed as the first argument,
328 with the remaining arguments passed as first, ... arguments.
329 .It Fn len arg
330 Returns the number of characters in the first argument.
331 Extra arguments
332 are ignored.
333 .It Fn m4exit code
334 Immediately exits with the return value specified by the first argument,
335 0 if none.
336 .It Fn m4wrap todo
337 Allows you to define what happens at the final
338 .Dv EOF ,
339 usually for cleanup purposes (e.g.,
340 .Ic m4wrap("cleanup(tempfile)")
341 causes the macro cleanup to be
342 invoked after all other processing is done).
343 .Pp
344 Multiple calls to
345 .Fn m4wrap
346 get inserted in sequence at the final
347 .Dv EOF .
348 .It Fn maketemp template
349 Invokes
350 .Xr mkstemp 3
351 on the first argument, and returns the modified string.
352 This can be used to create unique
353 temporary file names.
354 .It Fn paste file
355 Includes the contents of the file specified by the first argument without
356 any macro processing.
357 Aborts with an error message if the file cannot be
358 included.
359 .It Fn patsubst string regexp replacement
360 Substitutes a regular expression in a string with a replacement string.
361 Usual substitution patterns apply: an ampersand
362 .Pq Sq \&&
363 is replaced by the string matching the regular expression.
364 The string
365 .Sq \e# ,
366 where
367 .Sq #
368 is a digit, is replaced by the corresponding back-reference.
369 .It Fn popdef arg ...
370 Restores the
371 .Ic pushdef Ns ed
372 definition for each argument.
373 .It Fn pushdef macro def
374 Takes the same arguments as
375 .Ic define ,
376 but it saves the definition on a
377 stack for later retrieval by
378 .Fn popdef .
379 .It Fn regexp string regexp replacement
380 Finds a regular expression in a string.
381 If no further arguments are given,
382 it returns the first match position or \-1 if no match.
383 If a third argument
384 is provided, it returns the replacement string, with sub-patterns replaced.
385 .It Fn shift arg1 ...
386 Returns all but the first argument, the remaining arguments are
387 quoted and pushed back with commas in between.
388 The quoting
389 nullifies the effect of the extra scan that will subsequently be
390 performed.
391 .It Fn sinclude file
392 Similar to
393 .Ic include ,
394 except it ignores any errors.
395 .It Fn spaste file
396 Similar to
397 .Fn paste ,
398 except it ignores any errors.
399 .It Fn substr string offset length
400 Returns a substring of the first argument starting at the offset specified
401 by the second argument and the length specified by the third argument.
402 If no third argument is present it returns the rest of the string.
403 .It Fn syscmd cmd
404 Passes the first argument to the shell.
405 Nothing is returned.
406 .It Ic sysval
407 Returns the return value from the last
408 .Ic syscmd .
409 .It Fn traceon arg ...
410 Enables tracing of macro expansions for the given arguments, or for all
411 macros if no argument is given.
412 .It Fn traceoff arg ...
413 Disables tracing of macro expansions for the given arguments, or for all
414 macros if no argument is given.
415 .It Fn translit string mapfrom mapto
416 Transliterate the characters in the first argument from the set
417 given by the second argument to the set given by the third.
418 You cannot use
419 .Xr tr 1
420 style abbreviations.
421 .It Fn undefine name1 ...
422 Removes the definition for the macros specified by its arguments.
423 .It Fn undivert arg ...
424 Flushes the named output queues (or all queues if no arguments).
425 .It Ic unix
426 A pre-defined macro for testing the OS platform.
427 .It Ic __line__
428 Returns the current file's line number.
429 .It Ic __file__
430 Returns the current file's name.
431 .El
432 .Sh STANDARDS
433 The
434 .Nm
435 utility is compliant with the
436 .St -p1003.1-2008
437 specification.
438 .Pp
439 The flags
440 .Op Fl dgIot
441 and the macros
442 .Ic builtin ,
443 .Ic esyscmd ,
444 .Ic expr ,
445 .Ic format ,
446 .Ic indir ,
447 .Ic paste ,
448 .Ic patsubst ,
449 .Ic regexp ,
450 .Ic spaste ,
451 .Ic unix ,
452 .Ic __line__ ,
453 and
454 .Ic __file__
455 are extensions to that specification.
456 .Pp
457 The output format of tracing and of
458 .Ic dumpdef
459 are not specified in any standard,
460 are likely to change and should not be relied upon.
461 The current format of tracing is closely modelled on
462 .Nm gnu-m4 ,
463 to allow
464 .Nm autoconf
465 to work.
466 .Pp
467 The built-ins
468 .Ic pushdef
469 and
470 .Ic popdef
471 handle macro definitions as a stack.
472 However,
473 .Ic define
474 interacts with the stack in an undefined way.
475 In this implementation,
476 .Ic define
477 replaces the top-most definition only.
478 Other implementations may erase all definitions on the stack instead.
479 .Pp
480 All built-ins do expand without arguments in many other
481 .Nm m4 .
482 .Pp
483 Many other
484 .Nm
485 have dire size limitations with respect to buffer sizes.
486 .Sh AUTHORS
487 .An -nosplit
488 .An Ozan Yigit Aq oz@sis.yorku.ca
489 and
490 .An Richard A. O'Keefe Aq ok@goanna.cs.rmit.OZ.AU .
491 .Pp
492 GNU-m4 compatibility extensions by
493 .An Marc Espie Aq espie@cvs.openbsd.org .