m4(1) BSD Reference Manual m4(1)NAMEm4 - macro language processor
SYNOPSISm4 [-Dname[=value]] [-Uname] [-ce] [-o output-file] [input-files]
DESCRIPTION
The m4 utility is a macro processor that can be used as a front end to
any language (e.g., C, ratfor, Fortran, lex, and yacc). By default, m4
reads from the standard input and writes the processed text to the stan-
dard output.
Macro calls have the form name(argument1[, argument2, ...,] argumentN).
There cannot be any space following the macro name and the open parenthe-
ses '('. If the macro name is not followed by an open parentheses it is
processed with no arguments.
Macro names consist of a leading alphabetic or underscore possibly fol-
lowed by alphanumeric or underscore characters, therefore valid macro
names match this pattern [a-zA-Z_][a-zA-Z0-9_]*.
In arguments to macros, leading unquoted space, tab and newline charac-
ters are ignored. To quote strings use left and right single quotes
(e.g., ` this is a string with a leading space'). You can change the
quote characters with the changequote built-in macro.
The options are as follows:
-Dname[=value] Define the symbol name to have some value (or NULL).
-Uname Undefine the symbol name.
-c Toggles comment-stripping.
-e Enables interactive mode (ignores interrupt signals).
-o output-file Send output to the named output-file rather than the
standard output.
input-files Read the named input-files rather than the standard
input. The special file name ``-'' reads the standard
input at that point (this can be used to sandwich the
standard input between other files).
SYNTAXm4 provides the following built-in macros. They may be redefined, loos-
ing their original meaning. Return values are NULL unless otherwise
stated.
changecom Change the start and end comment sequences. The default
is the pound sign `#' and the newline character. With no
arguments comments are turned off. The maximum length
for a comment marker is five characters.
changequote Defines the quote symbols to be the first and second ar-
guments. The symbols may be up to five characters long.
If no arguments are given it restores the default open
and close single quotes.
decr Decrements the argument by 1. The argument must be a
valid numeric string.
define Define a new macro named by the first argument to have
the value of the second argument. Each occurrence of $n
(where n is 0 through 9) is replaced by the n'th argu-
ment. $0 is the name of the calling macro. Undefined
arguments are replaced by a NULL string. $# is replaced
by the number of arguments; $* is replaced by all argu-
ments comma separated; $@ is the same as $* but all argu-
ments are quoted against further expansion.
defn Returns the quoted definition for each argument. This
can be used to rename macro definitions (even for built-
in macros).
divert There are 10 output queues (numbered 0-9). At the end of
processing m4 concatenates all the queues in numerical
order to produce the final output. Initially the output
queue is 0. The divert macro allows you to select a new
output queue (an invalid argument passed to divert causes
output to be discarded).
divnum Returns the current output queue number.
dnl Discard input characters up to and including the next
newline.
dumpdef Prints the names and definitions for the named items, or
for everything if no arguments are passed.
errprint Prints the first argument on the standard error output
stream.
eval Computes the first argument as an arithmetic expression
using 32-bit arithmetic. Operators are the standard C
ternary, arithmetic, logical, shift, relational, bitwise,
and parentheses operators. You can specify octal, deci-
mal, and hexadecimal numbers as in C. The second argu-
ment (if any) specifies the radix for the result and the
third argument (if any) specifies the minimum number of
digits in the result.
expr This is an alias for eval.
ifdef If the macro named by the first argument is defined then
return the second argument, otherwise the third. If
there is no third argument, the value is NULL. The word
`unix' is predefined.
ifelse If the first argument matches the second argument then
ifelse returns the third argument. If the match fails
the three arguments are discarded and the next three ar-
guments are used until there is zero or one arguments
left, either this last argument or NULL is returned if no
other matches were found.
include Returns the contents of the file specified in the first
argument. Include aborts with an error message if the
file cannot be included.
incr Increments the argument by 1. The argument must be a
valid numeric string.
index Returns the index of the second argument in the first ar-
gument (e.g., index(the quick brown fox jumped, fox) re-
turns 16). If the second argument is not found index re-
turns -1.
len Returns the number of characters in the first argument.
Extra arguments are ignored.
m4exit Immediately exits with the return value specified by the
first argument, 0 if none.
m4wrap Allows you to define what happens at the final EOF, usu-
ally for cleanup purposes (e.g., m4wrap("cleanup(temp-
file)") causes the macro cleanup to invoked after all
other processing is done.)
maketemp Translates the string XXXXX in the first argument with
the current process ID leaving other characters alone.
This can be used to create unique temporary file names.
paste Includes the contents of the file specified by the first
argument without any macro processing. Aborts with an
error message if the file cannot be included.
popdef Restores the pushdef'ed definition for each argument.
pushdef Takes the same arguments as define, but it saves the def-
inition on a stack for later retrieval by popdef.
shift Returns all but the first argument, the remaining argu-
ments are quoted and pushed back with commas in between.
The quoting nullifies the effect of the extra scan that
will subsequently be performed.
sinclude Similar to include, except it ignores any errors.
spaste Similar to paste, except it ignores any errors.
substr Returns a substring of the first argument starting at the
offset specified by the second argument and the length
specified by the third argument. If no third argument is
present it returns the rest of the string.
syscmd Passes the first argument to the shell. Nothing is re-
turned.
sysval Returns the return value from the last syscmd.
translit Transliterate the characters in the first argument from
the set given by the second argument to the set given by
the third. You cannot use tr(1) style abbreviations.
undefine Removes the definition for the macro specified by the
first argument.
undivert Flushes the named output queues (or all queues if no ar-
guments).
unix A pre-defined macro for testing the OS platform.
AUTHOR
Ozan Yigit <oz@sis.yorku.ca> and Richard A. O'Keefe (ok@goan-
na.cs.rmit.OZ.AU)
BSDI BSD/OS January 26, 1993 3
