m4(1) CLIX m4(1)
NAME
m4 - Runs a macro processor
SYNOPSIS
m4 [flag ... ] [file ... ]
FLAGS
-e Operates interactively. Interrupts are ignored and the output is
unbuffered.
-s Enables line sync output for the C preprocessor (#line ...)
-Bint Changes the size of the push-back and argument collection buffers
from the default of 4,096.
-Hint Changes the size of the symbol table hash array from the default
of 199. The size should be a prime number.
-Sint Changes the size of the call stack from the default of 100 slots.
Macros take three slots, and nonmacro arguments take one.
-Tint Changes the size of the token buffer from the default of 512
bytes.
To be effective, these flags must appear before any filenames and before
any -D or -U flags, which are described as follows:
-Dname[=val] Defines name to have the value val, or null in the absence
of val.
-Uname Removes the definition of name.
DESCRIPTION
The m4 command 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 filename is -, stdin is read. The processed
text is written on stdout.
Macro calls have the following form:
name(arg1, arg2, ... , argn)
The ( must immediately follow the name of the macro. If the name of a
defined macro is not followed by a (, it is deemed to be a call of that
macro with no arguments. Potential macro names consist of alphabetic
letters, digits, and underscore (_), where the first character is not a
digit.
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m4(1) CLIX m4(1)
Leading unquoted blanks, tabs, and newlines 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 the quotes.
When a macro name is recognized, its arguments are collected by searching
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.
The m4 command makes available the following built-in macros. They may be
redefined, but once this is done the original meaning is lost. Their
values are null unless otherwise stated.
define Installs the second argument 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 nth
argument. Argument 0 is the name of the macro; missing
arguments are replaced by the null string; $# 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 quotes).
undefine Removes the definition of the macro named in its argument.
defn Returns the quoted definition of its argument(s). It is
useful for renaming macros, especially built-in ones.
pushdef Acts like define, but saves any previous definition.
popdef Removes current definition of its argument(s), exposing the
previous one, if any.
ifdef Has up to three arguments. If the first argument is
defined, the value is the second argument, otherwise the
third. If there is no third argument, the value is null.
The word unix is predefined on UNIX system versions of m4.
shift Returns all but its 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
subsequently be performed.
changequote Changes quote symbols to the first and second arguments.
The symbols may be up to five characters long. Using
changequote without arguments restores the original values
(that is, `').
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m4(1) CLIX m4(1)
changecom Changes 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.
divert The m4 command 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 its
(digit-string) argument. Output diverted to a stream other
than 0 through 9 is discarded.
undivert Causes 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 Returns the value of the current output stream.
dnl Reads and discards characters up to and including the next
newline.
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
arguments, the process is repeated with arguments 4, 5, 6
and 7. Otherwise, the value is either the fourth string,
or, if it is not present, null.
incr Returns the value of its argument incremented by 1. The
value of the argument is calculated by interpreting an
initial digit-string as a decimal number.
decr Returns the value of its argument decremented by 1.
eval Evaluates its argument as an arithmetic expression, using
32-bit arithmetic. Operators include +, -, *, /, % , ^
(exponentiation), bitwise &, |, ^, and ~, relationals, and
parentheses. Octal 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.
len Returns the number of characters in its argument.
index Returns the position in its first argument where the second
argument begins (zero origin), or -1 if the second argument
does not occur.
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substr Returns a substring of its first argument. The second
argument 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 Transliterates the characters in its first argument from the
set given by the second argument to the set given by the
third. No abbreviations are permitted.
include Returns the contents of the file named in the argument.
sinclude Is identical to include, except that it says nothing if the
file is inaccessible.
syscmd Executes the CLIX system command given in the first
argument. No value is returned.
sysval Is the return code from the last call to syscmd.
maketemp Fills in a string of XXXXX in its argument with the current
process ID.
m4exit Causes immediate exit from m4. Argument 1, if given, is the
exit code; the default is 0.
m4wrap Pushes argument 1 back at the EOF. For example:
m4wrap(`cleanup()').
errprint Displays its argument on the diagnostic output file.
dumpdef Displays current names and definitions, for the named items,
or for all if no arguments are given.
traceon With no arguments, turns on tracing for all macros
(including built-in ones). Otherwise, turns on tracing for
named macros.
traceoff Turns off trace globally and for any macros specified.
Macros specifically traced by traceon can be untraced only
by specific calls to traceoff.
EXIT VALUES
Exits with 0 if successful.
RELATED INFORMATION
Commands: acc(1), cc(1), cpp(1)
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