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8 .\" Ozan Yigit at York University.
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39 .Nd macro language processor
45 .Fl D Ar name Op No = Ar value
48 .Op Fl d Oo Oo +- Oc Ns Ar flags Oc
57 utility is a macro processor that can be used as a front end to any
58 language (e.g., C, ratfor, fortran, lex, and yacc).
59 If no input files are given,
61 reads from the standard input,
62 otherwise files specified on the command line are
63 processed in the given order.
64 Input files can be regular files, files in the m4 include paths, or a
67 denoting standard input.
70 the processed text to the standard output, unless told otherwise.
72 Macro calls have the form name(argument1[, argument2, ..., argumentN]).
74 There cannot be any space following the macro name and the open
77 If the macro name is not followed by an open
78 parenthesis it is processed with no arguments.
80 Macro names consist of a leading alphabetic or underscore
81 possibly followed by alphanumeric or underscore characters, e.g.,
82 valid macro names match the pattern
83 .Dq [a-zA-Z_][a-zA-Z0-9_]* .
85 In arguments to macros, leading unquoted space, tab, and newline
87 characters are ignored.
88 To quote strings, use left and right single quotes
89 .Pq e.g., Sq \ \&this is a string with a leading space .
90 You can change the quote characters with the
94 Most built-ins do not make any sense without arguments, and hence are not
95 recognized as special when not followed by an open parenthesis.
97 The options are as follows:
99 .It Fl D Ns Ar name Ns Oo = Ns Ar value Oc , Fl -define Ns = Ns Ar name Ns Oo = Ns Ar value Oc
102 to have some value (or
104 .It Fl d Oo Oo +|- Oc Ns Ar flags Oc , Fl -debug Ns = Ns Oo Oo +|- Oc Ns Ar flags Oc
105 Set or unset trace flags.
106 The trace flags are as follows:
109 print macro arguments.
111 print macro expansion over several lines.
113 print result of macro expansion.
115 print filename location.
119 quote arguments and expansion with the current quotes.
121 start with all macros traced.
123 number macro expansions.
132 is used, the specified flags are added to or removed from the set of
133 active trace flags, respectively; otherwise, the specified flags
134 replace the set of active trace flags.
136 Specifying this option without an argument is equivalent to specifying
140 By default, trace is set to
142 .It Fl E , Fl -fatal-warnings
143 Set warnings to be fatal.
146 flag is specified, if warnings are issued, execution
149 will exit with a non-zero exit status.
152 flags are specified, execution will halt upon issuing the
155 will exit with a non-zero exit status.
156 This behavior matches GNU m4 1.4.9 and later.
157 .It Fl G , Fl -traditional
158 Disable GNU compatibility mode (see
162 Enable GNU compatibility mode.
165 handles simple character ranges (e.g.,
167 regular expressions mimic Emacs behavior,
170 calls are handled as a stack,
171 the number of diversions is unlimited,
172 empty names for macro definitions are allowed,
174 can be used to include files,
180 .It Fl I Ar dirname , Fl -include Ns = Ns Ar dirname
184 .It Fl o Ar filename , Fl -error-output Ns = Ns Ar filename
187 .It Fl P , Fl -prefix-builtins
188 Prefix all built-in macros with
190 For example, instead of writing
194 .It Fl s , Fl -synclines
195 Output line synchronization directives, suitable for
197 .It Fl t Ar macro , Fl -trace Ns = Ns Ar macro
200 .It Fl U Ns Ar name , Fl -undefine Ns = Ns Ar name
206 provides the following built-in macros.
207 They may be redefined, losing their original meaning.
208 Return values are null unless otherwise stated.
209 .Bl -tag -width changequote
211 Calls a built-in by its
213 overriding possible redefinitions.
214 .It Fn changecom startcomment endcomment
215 Changes the start comment and end comment sequences.
216 Comment sequences may be up to five characters long.
217 The default values are the hash sign
218 and the newline character.
219 .Bd -literal -offset indent
223 With no arguments, comments are turned off.
224 With one single argument, the end comment sequence is set
225 to the newline character.
226 .It Fn changequote beginquote endquote
227 Defines the open quote and close quote sequences.
228 Quote sequences may be up to five characters long.
229 The default values are the backquote character and the quote
231 .Bd -literal -offset indent
232 `Here is a quoted string'
235 With no arguments, the default quotes are restored.
236 With one single argument, the close quote sequence is set
237 to the newline character.
239 Decrements the argument
244 must be a valid numeric string.
245 .It Fn define name value
246 Define a new macro named by the first argument
249 value of the second argument
255 is 0 through 9) is replaced by the
259 is the name of the calling macro.
260 Undefined arguments are replaced by a null string.
262 is replaced by the number of arguments;
264 is replaced by all arguments comma separated;
268 but all arguments are quoted against further expansion.
270 Returns the quoted definition for each argument.
271 This can be used to rename
272 macro definitions (even for built-in macros).
274 There are 10 output queues (numbered 0-9).
275 At the end of processing
277 concatenates all the queues in numerical order to produce the
279 Initially the output queue is 0.
281 macro allows you to select a new output queue (an invalid argument
282 passed to divert causes output to be discarded).
284 Returns the current output queue number.
286 Discard input characters up to and including the next newline.
287 .It Fn dumpdef name ...
288 Prints the names and definitions for the named items, or for everything
289 if no arguments are passed.
291 Prints the first argument on the standard error output stream.
293 Passes its first argument to a shell and returns the shell's standard output.
294 Note that the shell shares its standard input and standard error with
296 .It Fn eval expr[,radix[,minimum]]
297 Computes the first argument as an arithmetic expression using 32-bit
299 Operators are the standard C ternary, arithmetic, logical,
300 shift, relational, bitwise, and parentheses operators.
302 octal, decimal, and hexadecimal numbers as in C.
303 The optional second argument
305 specifies the radix for the result and the optional third argument
307 specifies the minimum number of digits in the result.
311 .It Fn format formatstring arg1 ...
314 with escape sequences substituted with
316 and following arguments, in a way similar to
318 This built-in is only available in GNU-m4 compatibility mode, and the only
319 parameters implemented are there for autoconf compatibility:
320 left-padding flag, an optional field width, a maximum field width,
321 *-specified field widths, and the %s and %c data type.
322 .It Fn ifdef name yes no
323 If the macro named by the first argument is defined then return the second
324 argument, otherwise the third.
325 If there is no third argument, the value is
330 .It Fn ifelse a b yes ...
331 If the first argument
333 matches the second argument
340 If the match fails the three arguments are
341 discarded and the next three arguments are used until there is
342 zero or one arguments left, either this last argument or
344 is returned if no other matches were found.
346 Returns the contents of the file specified in the first argument.
347 If the file is not found as is, look through the include path:
348 first the directories specified with
350 on the command line, then the environment variable
352 as a colon-separated list of directories.
353 Include aborts with an error message if the file cannot be included.
355 Increments the argument by 1.
356 The argument must be a valid numeric string.
357 .It Fn index string substring
358 Returns the index of the second argument in the first argument (e.g.,
359 .Ic index(the quick brown fox jumped, fox)
362 argument is not found index returns \-1.
363 .It Fn indir macro arg1 ...
364 Indirectly calls the macro whose name is passed as the first argument,
365 with the remaining arguments passed as first, ... arguments.
367 Returns the number of characters in the first argument.
371 Immediately exits with the return value specified by the first argument,
374 Allows you to define what happens at the final
376 usually for cleanup purposes (e.g.,
377 .Ic m4wrap("cleanup(tempfile)")
378 causes the macro cleanup to be
379 invoked after all other processing is done).
383 get inserted in sequence at the final
385 .It Fn maketemp template
388 .It Fn mkstemp template
391 on the first argument, and returns the modified string.
392 This can be used to create unique
393 temporary file names.
395 Includes the contents of the file specified by the first argument without
396 any macro processing.
397 Aborts with an error message if the file cannot be
399 .It Fn patsubst string regexp replacement
400 Substitutes a regular expression in a string with a replacement string.
401 Usual substitution patterns apply: an ampersand
403 is replaced by the string matching the regular expression.
408 is a digit, is replaced by the corresponding back-reference.
409 .It Fn popdef arg ...
412 definition for each argument.
413 .It Fn pushdef macro def
414 Takes the same arguments as
416 but it saves the definition on a
417 stack for later retrieval by
419 .It Fn regexp string regexp replacement
420 Finds a regular expression in a string.
421 If no further arguments are given,
422 it returns the first match position or \-1 if no match.
424 is provided, it returns the replacement string, with sub-patterns replaced.
425 .It Fn shift arg1 ...
426 Returns all but the first argument, the remaining arguments are
427 quoted and pushed back with commas in between.
429 nullifies the effect of the extra scan that will subsequently be
434 except it ignores any errors.
438 except it ignores any errors.
439 .It Fn substr string offset length
440 Returns a substring of the first argument starting at the offset specified
441 by the second argument and the length specified by the third argument.
442 If no third argument is present it returns the rest of the string.
444 Passes the first argument to the shell.
447 Returns the return value from the last
449 .It Fn traceon arg ...
450 Enables tracing of macro expansions for the given arguments, or for all
451 macros if no argument is given.
452 .It Fn traceoff arg ...
453 Disables tracing of macro expansions for the given arguments, or for all
454 macros if no argument is given.
455 .It Fn translit string mapfrom mapto
456 Transliterate the characters in the first argument from the set
457 given by the second argument to the set given by the third.
461 .It Fn undefine name1 ...
462 Removes the definition for the macros specified by its arguments.
463 .It Fn undivert arg ...
464 Flushes the named output queues (or all queues if no arguments).
466 A pre-defined macro for testing the OS platform.
468 Returns the current file's line number.
470 Returns the current file's name.
477 macro can modify the exit status, as can the
485 .%I AT&T Bell Laboratories
486 .%T The M4 Macro Processor
487 .%R Computing Science Technical Report
494 utility is compliant with the
514 are extensions to that specification.
517 is not supposed to be a synonym for
519 but instead to be an insecure temporary file name creation function.
522 as being obsolescent and should not be used if portability is a concern.
528 are not specified in any standard,
529 are likely to change and should not be relied upon.
530 The current format of tracing is closely modelled on
540 handle macro definitions as a stack.
543 interacts with the stack in an undefined way.
544 In this implementation,
546 replaces the top-most definition only.
547 Other implementations may erase all definitions on the stack instead.
549 All built-ins do expand without arguments in many other
554 have dire size limitations with respect to buffer sizes.
557 .An Ozan Yigit Aq Mt oz@sis.yorku.ca
559 .An Richard A. O'Keefe Aq Mt ok@goanna.cs.rmit.OZ.AU .
561 GNU-m4 compatibility extensions by
562 .An Marc Espie Aq Mt espie@cvs.openbsd.org .