.TH M4 1 .SH NAMEm4 \- macro processor.SH SYNOPSIS.B m4[ files ].SH DESCRIPTION.I M4is a macro processorintended as a front end for Ratfor, C, and other languages.Each of the argument files is processed in order;if there are no arguments, or if an argument is `\-',the standard input is read.The processed text is written on the standard output..PPMacro callshave the form.PP	name(arg1,arg2, . . . , argn).br.PPThe `(' must immediately follow the name of the macro.If a defined macro name is not followed by a `(',it is deemed to have no arguments.Leading unquoted blanks, tabs, and newlines are ignored while collecting arguments.Potential macro names consist of alphabetic letters,digits, and underscore `\_', where the first character is not a digit..PPLeft and right single quotes (\`\|\') are used to quote strings.The value of a quoted string is the string stripped of the quotes..PPWhen a macro name is recognized,its arguments are collected by searching for a matching rightparenthesis.Macro evaluation proceeds normally during the collection of the arguments,and any commas or right parentheseswhich happen to turn up within the value of a nestedcall are as effective as those in the original input text.After argument collection,the value of the macro is pushed back onto the input streamand rescanned..PP.I M4makes 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..TP 10defineThe second argument is installed as the value of the macrowhose name is the first argument.Each occurrence of $\fIn\fR in the replacement text,where.I nis a digit,is replaced by the.IR n -thargument.Argument 0 is the name of the macro;missing arguments are replaced by the null string..TPundefineremoves the definition of the macro named in its argument..TPifdefIf 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.I unixis predefined on UNIX versions of.IR m4 ..TPchangequoteChange quote characters to the first and second arguments..I Changequotewithout arguments restores the original values(i.e., \`\|\')..TPdivert.I M4maintains 10 output streams,numbered 0-9.The final output is the concatenation of the streamsin numerical order;initially stream 0 is the current stream.The.I divertmacro changes the current output stream to its (digit-string)argument.Output diverted to a stream other than 0 through 9is discarded..TPundivertcauses immediate output of text from diversions named asarguments, or all diversions if no argument.Text may be undiverted into another diversion.Undiverting discards the diverted text..TPdivnumreturns the value of the current output stream..TPdnlreads and discards characters up to and including the next newline..TPifelsehas 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..TPincrreturns the value of its argument incremented by 1.The value of the argument is calculatedby interpreting an initial digit-string as a decimal number..TPevalevaluates its argument as an arithmetic expression, using 32-bit arithmetic.Operators include +, \-, \(**, /, %, ^ (exponentiation); relationals; parentheses..TPlenreturns the number of characters in its argument..TPindexreturns the position in its first argument where the second argument begins (zero origin),or \-1 if the second argument does not occur..TPsubstrreturns a substring of its first argument.The second argument is a zero originnumber 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 tothe end of the first string..TPtranslittransliterates the characters in its first argumentfrom the set given by the second argument to the set given by the third.No abbreviations are permitted..TPincludereturns the contents of the file named in the argument..TPsincludeis identical to.I include,except that itsays nothing if the file is inaccessible..TPsyscmdexecutes the UNIX command given in the first argument.No value is returned..TPmaketempfills in a string of XXXXX in its argument with the current process id..TPerrprintprints its argumenton the diagnostic output file..TPdumpdefprints current names and definitions,for the named items, or for all if no arguments are given..dt.SH "SEE ALSO"B. W. Kernighan and D. M. Ritchie,.I The M4 Macro Processor