m4 - macro language processor
m4 [ filename ] ...
SYSTEM V SYNOPSIS
/usr/5bin/m4 [ -es ] [ -Bint ] [ -Hint ] [ -Sint ] [ -Tint ] [
-Dname=val ] [ -Uname ] [ filename ]...
The System V version of this command is available with the System V
software installation option. Refer to for information on how to
install optional software.
m4 is a macro processor intended as a front end for Ratfor, C, and
other languages. Each of the argument files is processed in order; if
there are no files, or if a file name is `-', the standard input is
read. The processed text is written on the standard output.
Macro calls have the form:
name(argument1[, argument2, ...,] argumentn)
The `(' must immediately follow the name of the macro. If the name of
a defined macro is not followed by a `(', it is interpreted as a call
of the macro with no arguments. Potential macro names consist of let-
ters, digits, and `_', (underscores) where the first character is not a
Leading unquoted SPACE, TAB, and NEWLINE characters are ignored while
collecting arguments. Left and right single quotes (`') are used to
quote strings. The value of a quoted string is the string stripped of
When a macro name is recognized, the arguments are collected by search-
ing for a matching right parenthesis. If fewer arguments are supplied
than are in the macro definition, the trailing arguments are taken to
be NULL. Macro evaluation proceeds normally during the collection of
the arguments, and any commas or right parentheses which happen to turn
up within the value of a nested call are as effective as those in the
original input text. After argument collection, the value of the macro
is pushed back onto the input stream and rescanned.
SYSTEM V OPTIONS
The options and their effects are as follows:
-e Operate interactively. Interrupts are ignored and the output is
-s Enable line sync output for the C preprocessor (#line ...)
-Bint Change the size of the push-back and argument collection buffers
from the default of 4,096.
-Hint Change the size of the symbol table hash array from the default
of 199. The size should be prime.
-Sint Change the size of the call stack from the default of 100 slots.
Macros take three slots, and non-macro arguments take one.
-Tint Change the size of the token buffer from the default of 512
To be effective, these flags must appear before any file names and
before any -D or -U flags:
Define filename to be val or to be NULL in val's absence.
-Uname Undefine name.
m4 makes available the following built-in macros. They may be rede-
fined, but once this is done the original meaning is lost. Their val-
ues are NULL unless otherwise stated.
define The second argument is installed as the value of the macro
whose name is the first argument. Each occurrence of $n in
the replacement text, where n is a digit, is replaced by
the n'th argument. Argument 0 is the name of the macro;
missing arguments are replaced by the NULL string.
undefine Remove the definition of the macro named in the argument.
ifdef If the first argument is defined, the value is the second
argument, otherwise the third. If there is no third argu-
ment, the value is NULL. The word unix is predefined.
changequote Change quote characters to the first and second arguments.
changequote without arguments restores the original values
(that is, `').
divert m4 maintains 10 output streams, numbered 0-9. The final
output is the concatenation of the streams in numerical
order; initially stream 0 is the current stream. The
divert macro changes the current output stream to the
(digit-string) argument. Output diverted to a stream other
than 0 through 9 is discarded.
undivert Display immediate output of text from diversions named as
arguments, or all diversions if no argument. Text may be
undiverted into another diversion. Undiverting discards
the diverted text.
divnum Return the value of the current output stream.
dnl Read and discard characters up to and including the next
ifelse Has three or more arguments. If the first argument is the
same string as the second, then the value is the third
argument. If not, and if there are more than four argu-
ments, the process is repeated with arguments 4, 5, 6, 7
and so on. Otherwise, the value is either the last string
not used by the above process, or, if it is not present,
incr Return the value of the argument incremented by 1. The
value of the argument is calculated by interpreting an ini-
tial digit-string as a decimal number.
eval Evaluate the argument as an arithmetic expression, using
32-bit arithmetic. Operators include +, -, *, /, %, ^
(exponentiation); relationals; parentheses.
len Return the number of characters in the argument.
index Return the position in the first argument where the second
argument begins (zero origin), or -1 if the second argument
does not occur.
substr Return a substring of the first argument. The second argu-
ment is a zero origin number selecting the first character;
the third argument indicates the length of the substring.
A missing third argument is taken to be large enough to
extend to the end of the first string.
translit Transliterate the characters in the first argument from the
set given by the second argument to the set given by the
third. No abbreviations are permitted.
include Return the contents of the file named in the argument.
sinclude Is similar to include, except that it says nothing if the
file is inaccessible.
syscmd Execute the system command given in the first argument. No
value is returned.
maketemp Fill in a string of XXXXX in the argument with the current
errprint Print the argument on the diagnostic output file.
dumpdef Print current names and definitions, for the named items,
or for all if no arguments are given.
SYSTEM V USAGE
In the System V version of m4, the following built-in macros have added
define `$#' is replaced by the number of arguments; $* is replaced
by a list of all the arguments separated by commas; $@ is
like `$*', but each argument is quoted (with the current
changequote Change quote symbols to the first and second arguments.
The symbols may be up to five characters long.
eval Additional operators include bitwise `&&', `|', `^' and `~'.
Octal, decimal and hex numbers may be specified as in C.
The second argument specifies the radix for the result; the
default is 10. The third argument may be used to specify
the minimum number of digits in the result.
The System V version of m4 makes available the following additional
defn Return the quoted definition of the argument(s). It is
useful for renaming macros, especially built-ins.
pushdef Like define, but saves any previous definition.
popdef Remove current definition of the argument(s), exposing the
previous one, if any.
shift Return all but the first argument. The other arguments are
quoted and pushed back with commas in between. The quoting
nullifies the effect of the extra scan that will subse-
quently be performed.
changecom Change left and right comment markers from the default #
and NEWLINE. With no arguments, the comment mechanism is
effectively disabled. With one argument, the left marker
becomes the argument and the right marker becomes NEWLINE.
With two arguments, both markers are affected. Comment
markers may be up to five characters long.
decr Return the value of the argument decremented by 1.
sysval Return code from the last call to syscmd.
m4exit Exit immediately from m4. Argument 1, if given, is the
exit code; the default is 0.
m4wrap Argument 1 will be pushed back at final EOF. For example,
traceon With no arguments, turn on tracing for all macros (includ-
ing built-ins). Otherwise, turn on tracing for named
traceoff Turn off trace globally and for any macros specified.
Macros specifically traced by traceon can be untraced only
by specific calls to traceoff.
m4 -- A Macro Processor, in
While the compiler allows 8-bit strings and comments, 8-bits are not
allowed anywhere else. The cc(1V) command does not generate or support
8-bit symbol names because, until ANSI C, non-ASCII support was not
expected. The ANSI C specification now suggests that string literals
and comments can contain any characters from any character code set.
23 September 1987 M4(1V)