Minix2.0/man/man9/m4.9
.CD "m4 \(en macro processor"
.SX "m4\fR [\fB\(enD \fIname\fR = \fIvalue\fR]\fR [\fB\(enU \fIname\fR]
.FL "\(enD" "Define a symbol"
.FL "\(enU" "Undefine a symbol"
.EY "m4 <m4test" "Run M4"
.PP
\fIM4\fR is a macro processor intended as a front end
for Ratfor, Pascal, and other languages that do not have a built-in macro
processing capability. M4 reads standard input, the processed text is
written on the standard output.
.PP
The options and their effects are as follows:
.in +0.5i
.ta 1.25i
\(enD name[=val] Defines name to val, or to null in val's absence.
.br
\(enU name Undefines name.
.in -0.5i
.PP
Macro calls have the form: name(arg1,arg2, ..., argn)
The \*(OQ(\*(CQ must immediately follow the name of the macro.
If the name of a
defined macro is not followed by a ( it is taken to be a call of that macro
with no arguments, i.e. name(). Potential macro names consist of alphabetic
letters and digits.
.PP
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.
.PP
When a macro name is recognized, its arguments are collected by searching
for a matching ). 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. (This is typically
referred as inside-out macro expansion.) After argument collection, the
value of the macro is pushed back onto the input stream and rescanned.
.PP
M4 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.
.PP
\fBdefine "(name [, val])"\fR the second argument is installed as the value of
the macro whose name is the first argument. If there is no second argument,
the value is null. 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.
.PP
\fBdefn "(name [, name ...])"\fR returns the quoted definition of its
argument(s). Useful in renaming macros.
.PP
\fBundefine "(name [, name ...])"\fR removes the definition of the macro(s)
named. If there is more than one definition for the named macro, (due to
previous use of pushdef) all definitions are removed.
.PP
\fBpushdef "(name [, val])"\fR like define, but saves any previous definition
by stacking the current definition.
.PP
\fBpopdef "(name [, name ...])"\fR removes current definition of its
argument(s), exposing the previous one if any.
.PP
\fBifdef "(name, if-def [, ifnot-def])"\fR 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. A word indicating the current operating system
is predefined. (e.g. unix or vms).
.PP
\fBshift "(arg, arg, arg, ...)"\fR 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.
.PP
\fBchangequote "(lqchar, rqchar)"\fR change quote symbols to the first and
second arguments. With no arguments, the quotes are reset back to the default
characters. (i.e., `').
.PP
\fBchangecom "(lcchar, rcchar)"\fR change left and right comment markers from
the default # and newline. With no arguments, the comment mechanism is reset
back to the default characters. With one argument, the left marker becomes
the argument and the right marker becomes newline. With two arguments, both
markers are affected.
.PP
\fBdivert "(divnum)"\fR maintains 10 output streams, numbered 0-9. 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 lost.
.PP
\fBundivert "([divnum [, divnum ...]])"\fR causes immediate output of text from
diversions named as argument(s), or all diversions if no argument. Text may
be undiverted into another diversion. Undiverting discards the diverted text.
At the end of input processing, M4 forces an automatic undivert unless is
defined.
.PP
\fBdivnum "()"\fR returns the value of the current output stream.
.PP
\fBdnl "()"\fR reads and discards characters up to and including the next
newline.
.PP
\fBifelse "(arg, arg, if-same [, ifnot-same | arg, arg ...])"\fR 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.
.PP
\fBincr "(num)"\fR 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.
.PP
\fBdecr "(num)"\fR returns the value of its argument decremented by 1.
.PP
\fBeval "(expression)"\fR evaluates its argument as a constant expression,
using integer arithmetic. The evaluation mechanism is very similar to that of
cpp (#if expression). The expression can involve only integer constants and
character constants, possibly connected by the binary operators
.HS
.in +0.5i
* / % + - >> << < > <= >= == != & ^ | && ||
.in -0.5i
.HS
or the unary operators - ! or tilde or by the ternary operator ? : .
Parentheses may be used for grouping. Octal numbers may be specified as in C.
.PP
\fBlen "(string)"\fR returns the number of characters in its argument.
.PP
\fBindex "(search-string, string)"\fR returns the position in its first
argument where the second argument begins (zero origin), or 1 if the second
argument does not occur.
.PP
\fBsubstr "(string, index [, length])"\fR returns a substring of its first
argument. The second argument is a zero origin number selecting the first
character (internally treated as an expression); 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.
.PP
\fBtranslit "(source, from [, to])"\fR transliterates the characters in its
first argument from the set given by the second argument to the set given by
the third. If the third argument is shorter than the second, all extra
characters in the second argument are deleted from the first argument. If the
third argument is missing altogether, all characters in the second argument
are deleted from the first argument.
.PP
\fBinclude "(filename)"\fR returns the contents of the file that is
named in the argument.
.PP
\fBsinclude "(filename)"\fRis identical to include, except that it says nothing
if the file is inaccessable.
.PP
\fBpaste "(filename)"\fR returns the contents of the file named in the argument
without any processing, unlike include.
.PP
\fBspaste "(filename)"\fR is identical to paste, except that it says nothing if
the file is inaccessibl[De.
.PP
\fBsyscmd "(command)"\fR executes the
.Ux
command given in the first argument.
No value is returned.
.PP
\fBsysval "()"\fR is the return code from the last call to syscmd.
.PP
\fBmaketemp \*(OQ(string)"\fR fills in a string of XXXXXX in its argument with the
current process ID.
.PP
\fBm4exit "([exitcode])"\fR causes immediate exit from M4. Argument 1, if
given, is the exit code; the default is 0.
.PP
\fBm4wrap "(m4-macro-or-built-n)"\fR argument 1 will be pushed back at final
EOF; example: m4wrap(`dumptable()').
.PP
\fBerrprint "(str [, str, str, ...])"\fR prints its argument(s) on stderr. If
there is more than one argument, each argument is separated by a space during
the output. An arbitrary number of arguments may be supplied.
.PP
\fBdumpdef "([name, name, ...])"\fR prints current names and definitions, for
the named items, or for all if no arguments are given.
.SP 1
.SS "Author"
.SP 1
.PP
\fIM4\fR was written by Ozan S. Yigif.