Tribblix: manual page: m4.1

M4(1) User Commands M4(1)

NAME

m4 - 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 message 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
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.

Macro Processing

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 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
buffers 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. changequote 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 NEWLINE. 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
second argument, otherwise the third. If there is no
third argument, the value is NULL. The word unix is
predefined.

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
second 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
argument. 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
tracing for named macros.

traceoff
Turns off trace globally and for any macros specified.

undefine
Removes the definition of the macro named in its
argument.

undivert
This macro causes immediate output of text from
diversions named as arguments, or all diversions if no
argument. 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(7) 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