.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.
