1m4(1) General Commands Manual m4(1)
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6 m4 - macro processor
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9 m4 [ -Dname[=value]] [-Uname] [files ...]
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12 m4 is a macro processor intended as a front end for any language (e.g.,
13 C, ratfor, fortran, lex, and yacc). m4 reads from the standard input
14 and writes the processed text to the standard output. Each of the
15 optional argument files is processed in order.
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 -Dname[=value]
39 Define the symbol name to have some value (or NULL).
40 -Uname Undefine the symbol name.
42 m4 makes available the following built-in macros. They may be rede‐
44 fined, but once this is done the original meaning is lost. Their val‐
45 ues are null unless otherwise stated.
46 define The second argument is installed as the value of the macro
48 whose name is the first argument. Each occurrence of $n in
49 the replacement text, where n is a digit, is replaced by the
50 n-th argument. Argument 0 is the name of the macro; missing
51 arguments are replaced by the null string.
52 undefine removes the definition of the macro named in its argument.
54 ifdef If the first argument is defined, the value is the second
56 argument, otherwise the third. If there is no third argu‐
57 ment, the value is null.
58 changecom Change the start and end comment sequences. The default is
60 the pound sign '#' and the newline character. With no argu‐
61 ments comments are turned off. The maximum legnth for a com‐
62 ment marker is five characters.
63 changequote
65 Change quote characters to the first and second arguments.
66 Changequote without arguments restores the original values
67 (i.e., `´).
68 decr Decrements the argument by 1. The argument must be a valid
70 numeric string.
71 divert m4 maintains 10 output streams, numbered 0-9. The final out‐
73 put is the concatenation of the streams in numerical order;
74 initially stream 0 is the current stream. The divert macro
75 changes the current output stream to its (digit-string) argu‐
76 ment. Output diverted to a stream other than 0 through 9 is
77 discarded.
78 undivert causes immediate output of text from diversions named as
80 arguments, or all diversions if no argument. Text may be
81 undiverted into another diversion. Undiverting discards the
82 diverted text.
83 defn Returns the quoted definition for each argument. This can be
85 used to rename macro definitions (even for builtin macros).
86 divnum returns the value of the current output stream.
88 dnl reads and discards characters up to and including the next
90 newline.
91 expr This is an alias for eval.
93 ifelse has three or more arguments. If the first argument is the
95 same string as the second, then the value is the third argu‐
96 ment. If not, and if there are more than four arguments, the
97 process is repeated with arguments 4, 5, 6 and 7. Otherwise,
98 the value is either the fourth string, or, if it is not
99 present, null.
100 incr returns the value of its argument incremented by 1. The
102 value of the argument is calculated by interpreting an ini‐
103 tial digit-string as a decimal number.
104 eval evaluates its argument as an arithmetic expression, using
106 32-bit arithmetic. Operators include +, -, ∗, /, %, ^ (expo‐
107 nentiation); relationals; parentheses.
108 len returns the number of characters in its argument.
110 m4exit Immediately exits with the return value specified by the
112 first argument, 0 if none.
113 m4wrap Allows you to define what happens at the final EOF, usually
115 for cleanup purposes. (e.g., m4wrap("cleanup(tempfile)")
116 causes the macro cleanup to be invoked after all processing
117 is done.)
118 index returns the position in its first argument where the second
120 argument begins (zero origin), or -1 if the second argument
121 does not occur.
122 substr returns a substring of its first argument. The second argu‐
124 ment is a zero origin number selecting the first character;
125 the third argument indicates the length of the substring. A
126 missing third argument is taken to be large enough to extend
127 to the end of the first string.
128 translit transliterates the characters in its first argument from the
130 set given by the second argument to the set given by the
131 third. No abbreviations are permitted.
132 include returns the contents of the file named in the argument.
134 sinclude is identical to include, except that it says nothing if the
136 file is inaccessible.
137 syscmd executes the UNIX command given in the first argument. No
139 value is returned.
140 maketemp fills in a string of XXXXX in its argument with the current
142 process id.
143 paste Includes the contents of the file specified by the first
145 argument without any macro processing. Aborts with an error
146 message if the file cannot be included.
147 popdef Restores the pushdef'd definition for each argument.
149 pushdef Takes the same arguments as define, but it saves the defini‐
151 tion on a stack for later retrieval by popdef.
152 shift Returns all but the first argument, the remaining arguments
154 are quoted and pushed back with commas in between. The quot‐
155 ing nullifies the effect of the extra scan that will subse‐
156 quently be performed.
157 spaste Similar to paste, except it ignores any errors.
159 syscal Returns the return value from the last syscmd.
161 errprint prints its argument on the diagnostic output file.
163 dumpdef prints current names and definitions, for the named items, or
165 for all if no arguments are given.
166 unix A pre-defined macro for testing the OS platform.
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170 B. W. Kernighan and D. M. Ritchie, The m4 Macro Processor
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173 An m4 command appeared in Version 6 AT&T UNIX.
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176 Ozan Yigit <oz@sis.yorku.ca>
1773rd Berkeley Distribution April 14, 1994 m4(1)