M4(1)M4(1)NAMEm4 - macro processor
SYNOPSIS
/usr/bin/m4 [-e] [-s] [-B int] [-H int] [-S int]
[-T int] [-Dname [=val]] ... [-U name] ... [file]...
/usr/xpg4/bin/m4 [-e] [-s] [-B int] [-H int] [-S int]
[-T int] [-Dname [...=val]] [-U name] ... [file]...
DESCRIPTION
The m4 utility is a macro processor intended as a front end for C,
assembler, and other languages. Each of the argument files is processed
in order. If there are no files, or if a file is −, the standard input
is read. The processed text is written on the standard output. Note: m4
cannot include more than nine nested files and writes a diagnostic mes‐
sage if that number is exceeded.
Macro Syntax
Macro calls have the form:
name(arg1,arg2, ..., argn)
The open parenthesis character, (, 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 alphanumeric characters and underscore (_), where the
first character is not a digit.
Leading unquoted blanks, TABs, and NEWLINEs are ignored while collect‐
ing arguments. Left and right single quotes are used to quote strings.
The value of a quoted string is the string stripped of the quotes.
Macro Processing
When a macro name is recognized, its 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 that 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.
OPTIONS
The options and their effects are as follows:
-Bint
Changes the size of the push-back and argument collection buf‐
fers from the default of 4,096.
-e
Operates interactively. Interrupts are ignored and the output
is unbuffered.
-Hint
Changes the size of the symbol table hash array from the
default of 199. The size should be prime.
-s
Enables line sync output for the C preprocessor (#line ...)
-Sint
Changes the size of the call stack from the default of
100slots. Macros take three slots, and non-macro arguments
take one.
-Tint
Changes the size of the token buffer from the default of
512bytes.
To be effective, the above flags must appear before any file names and
before any -D or -U flags:
-D name[=val]
Defines name to val or to NULL in val's absence.
-Uname
Undefines name.
OPERANDS
The following operand is supported:
file
A path name of a text file to be processed. If no file is
given, or if it is −, the standard input is read.
USAGE
The m4 utility makes available the following built-in macros. These
macros can be redefined, but once this is done the original meaning is
lost. Their values are NULL unless otherwise stated.
changequote
Change quote symbols to the first and second arguments.
The symbols can be up to five characters long. change‐
quote without arguments restores the original values
(that is, `').
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 NEW‐
LINE. With two arguments, both markers are affected.
Comment markers can be up to five characters long.
decr
Returns the value of its argument decremented by 1.
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; $# 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).
defn
Returns the quoted definition of its argument(s). It is
useful for renaming macros, especially built-ins.
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 its
(digit-string) argument. Output diverted to a stream
other than 0 through 9 is discarded.
divnum
Returns the value of the current output stream.
dnl
Reads and discards characters up to and including the
next NEWLINE.
dumpdef
Prints current names and definitions, for the named
items, or for all if no arguments are given.
errprint
Prints its argument on the diagnostic output file.
ifdef
If the first argument is defined, the value is the sec‐
ond argument, otherwise the third. If there is no third
argument, the value is NULL. The word unix is prede‐
fined.
ifelse
This macro 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.
include
Returns the contents of the file named in the argument.
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.
index
Returns the position in its first argument where the
second argument begins (zero origin), or −1 if the sec‐
ond argument does not occur.
len
Returns the number of characters in its argument.
m4exit
This macro causes immediate exit from m4. Argument 1, if
given, is the exit code; the default is 0.
m4wrap
Argument 1 is pushed back at final EOF. Example:
m4wrap(`cleanup()')
maketemp
Fills in a string of "X" characters in its argument with
the current process ID.
popdef
Removes current definition of its argument(s), exposing
the previous one, if any.
pushdef
Like define, but saves any previous definition.
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 is
subsequently be performed.
sinclude
This macro is identical to include, except that it says
nothing if the file is inaccessible.
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.
syscmd
This macro executes the command given in the first argu‐
ment. No value is returned.
sysval
This macro is the return code from the last call to
syscmd.
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.
traceon
This macro with no arguments, turns on tracing for all
macros (including built-ins). Otherwise, turns on trac‐
ing for named macros.
traceoff
Turns off trace globally and for any macros specified.
undefine
Removes the definition of the macro named in its argu‐
ment.
undivert
This macro causes immediate output of text from diver‐
sions named as arguments, or all diversions if no argu‐
ment. Text can be undiverted into another diversion.
Undiverting discards the diverted text.
/usr/bin/m4
eval
Evaluates its argument as an arithmetic expression, using
32-bit signed-integer arithmetic. The following operators are
supported: parentheses, unary -, unary +, !, ~, *, /, %, +, -,
relationals, bitwise &, |, &&, and ||. Octal and hex numbers
can be specified as in C. The second argument specifies the
radix for the result; the default is 10. The third argument
can be used to specify the minimum number of digits in the
result.
/usr/xpg4/bin/m4
eval
Evaluates its argument as an arithmetic expression, using
32-bit signed-integer arithmetic. The following operators are
supported: parentheses, unary -, unary +, !, ~, *, /, %, +, -,
<<, >>, relationals, bitwise &, |, &&, and ||. Precedence and
associativity are as in C. Octal and hex numbers can also be
specified as in C. The second argument specifies the radix for
the result; the default is 10. The third argument can be used
to specify the minimum number of digits in the result.
EXAMPLES
Example 1 Examples of m4 files
If the file m4src contains the lines:
The value of `VER' is "VER".
ifdef(`VER', ``VER'' is defined to be VER., VER is not defined.)
ifelse(VER, 1, ``VER'' is `VER'.)
ifelse(VER, 2, ``VER'' is `VER'., ``VER'' is not 2.)
end
then the command:
m4 m4src
or the command:
m4-U VER m4src
produces the output:
The value of VER is "VER".
VER is not defined.
VER is not 2.
end
The command:
m4-D VER m4src
produces the output:
The value of VER is "".
VER is defined to be .
VER is not 2.
end
The command:
m4-D VER=1 m4src
produces the output:
The value of VER is "1".
VER is defined to be 1.
VER is 1.
VER is not 2.
end
The command:
m4-D VER=2 m4src
produces the output:
The value of VER is "2".
VER is defined to be 2.
VER is 2.
end
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of m4: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
and NLSPATH.
EXIT STATUS
The following exit values are returned:
0
Successful completion.
>0
An error occurred
If the m4exit macro is used, the exit value can be specified by the
input file.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
/usr/xpg4/bin/m4
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
└────────────────────┴─────────────────┘
SEE ALSOas(1), attributes(5), environ(5), standards(5)
Jul 3, 2007 M4(1)
