1M4(1) General Commands Manual M4(1)
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6 m4 - macro processor
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9 m4 [ files ]
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12 M4 is a macro processor intended as a front end for Ratfor, C, and
13 other languages. Each of the argument files is processed in order; if
14 there are no arguments, or if an argument is `-', the standard input is
15 read. The processed text is written on the standard output.
16 Macro calls have the form
18 name(arg1,arg2, . . . , argn)
20 The `(' must immediately follow the name of the macro. If a defined
22 macro name is not followed by a `(', it is deemed to have no arguments.
23 Leading unquoted blanks, tabs, and newlines are ignored while collect‐
24 ing arguments. Potential macro names consist of alphabetic letters,
25 digits, and underscore `_', where the first character is not a digit.
26 Left and right single quotes (`´) are used to quote strings. The value
28 of a quoted string is the string stripped of the quotes.
29 When a macro name is recognized, its arguments are collected by search‐
31 ing for a matching right parenthesis. Macro evaluation proceeds nor‐
32 mally during the collection of the arguments, and any commas or right
33 parentheses which happen to turn up within the value of a nested call
34 are as effective as those in the original input text. After argument
35 collection, the value of the macro is pushed back onto the input stream
36 and rescanned.
37 M4 makes available the following built-in macros. They may be rede‐
39 fined, but once this is done the original meaning is lost. Their val‐
40 ues are null unless otherwise stated.
41 define The second argument is installed as the value of the macro
43 whose name is the first argument. Each occurrence of $n in
44 the replacement text, where n is a digit, is replaced by the
45 n-th argument. Argument 0 is the name of the macro; missing
46 arguments are replaced by the null string.
47 undefine removes the definition of the macro named in its argument.
49 ifdef If the first argument is defined, the value is the second
51 argument, otherwise the third. If there is no third argu‐
52 ment, the value is null. The word unix is predefined on UNIX
53 versions of m4.
54 changequote
56 Change quote characters to the first and second arguments.
57 Changequote without arguments restores the original values
58 (i.e., `´).
59 divert M4 maintains 10 output streams, numbered 0-9. The final out‐
61 put is the concatenation of the streams in numerical order;
62 initially stream 0 is the current stream. The divert macro
63 changes the current output stream to its (digit-string) argu‐
64 ment. Output diverted to a stream other than 0 through 9 is
65 discarded.
66 undivert causes immediate output of text from diversions named as
68 arguments, or all diversions if no argument. Text may be
69 undiverted into another diversion. Undiverting discards the
70 diverted text.
71 divnum returns the value of the current output stream.
73 dnl reads and discards characters up to and including the next
75 newline.
76 ifelse has three or more arguments. If the first argument is the
78 same string as the second, then the value is the third argu‐
79 ment. If not, and if there are more than four arguments, the
80 process is repeated with arguments 4, 5, 6 and 7. Otherwise,
81 the value is either the fourth string, or, if it is not
82 present, null.
83 incr returns the value of its argument incremented by 1. The
85 value of the argument is calculated by interpreting an ini‐
86 tial digit-string as a decimal number.
87 eval evaluates its argument as an arithmetic expression, using
89 32-bit arithmetic. Operators include +, -, ∗, /, %, ^ (expo‐
90 nentiation); relationals; parentheses.
91 len returns the number of characters in its argument.
93 index returns the position in its first argument where the second
95 argument begins (zero origin), or -1 if the second argument
96 does not occur.
97 substr returns a substring of its first argument. The second argu‐
99 ment is a zero origin number selecting the first character;
100 the third argument indicates the length of the substring. A
101 missing third argument is taken to be large enough to extend
102 to the end of the first string.
103 translit transliterates the characters in its first argument from the
105 set given by the second argument to the set given by the
106 third. No abbreviations are permitted.
107 include returns the contents of the file named in the argument.
109 sinclude is identical to include, except that it says nothing if the
111 file is inaccessible.
112 syscmd executes the UNIX command given in the first argument. No
114 value is returned.
115 maketemp fills in a string of XXXXX in its argument with the current
117 process id.
118 errprint prints its argument on the diagnostic output file.
120 dumpdef prints current names and definitions, for the named items, or
122 for all if no arguments are given.
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125 B. W. Kernighan and D. M. Ritchie, The M4 Macro Processor
126 M4(1)