m4

The m4 utility is a macro processor that shall read one or more text files, process them according to their included macro statements, and write the results to standard output. Enable line synchronization output for the c99 preprocessor phase (that is, line directives). The input file named by the file operand shall be a text file. Provide a default value for the internationalization variables that are unset or null. (See XBD Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) If set to a non-empty string value, override the values of all the other internationalization variables. Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files). Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. [XSI) ] ![[Option Start]]( Determine the location of message catalogs for the processing of LC MESSAGES. ![[Option End]]( The standard output shall be the same as the input files, after being processed for macro expansion. The standard error shall be used to display strings with the errprint macro, macro tracing enabled by the traceon macro, the defined text for macros written by the dumpdef macro, or for diagnostic messages. The m4 utility shall compare each token from the input against the set of built-in and user-defined macros. If the token matches the name of a macro, then the token shall be replaced by the macro's defining text, if any, and rescanned for matching macro names. Once no portion of the token matches the name of a macro, it shall be written to standard output. Macros may have arguments, in which case the arguments shall be substituted into the defining text before it is rescanned. Macro names shall consist of letters, digits, and underscores, where the first character is not a digit. Tokens not of this form shall not be treated as macros. If a macro name is followed by a , its arguments are the -separated tokens between the and the matching . Unquoted white-space characters preceding each argument shall be ignored. All other characters, including trailing white-space characters, are retained. characters enclosed between and characters do not delimit arguments. No special meaning is given to any characters enclosed between matching left and right quoting strings, but the quoting strings are themselves discarded. By default, the left quoting string consists of a grave accent (backquote) and the right quoting string consists of an acute accent (single-quote); see also the changequote macro. Comments are written but not scanned for matching macro names; by default, the begin-comment string consists of the character and the end-comment string consists of a . See also the changecom and dnl macros. The m4 utility shall make available the following built-in macros. They can be redefined, but once this is done the original meaning is lost. Their values shall be null unless otherwise stated. In the descriptions below, the term defining text refers to the value of the macro: the second argument to the define macro, among other things. Except for the first argument to the eval macro, all numeric arguments to built-in macros shall be interpreted as decimal values. The string values produced as the defining text of the decr , divnum , incr , index , len , and sysval built-in macros shall be in the form of a decimal-constant as defined in the C language. The changecom macro shall set the begin-comment and end-comment strings. With no arguments, the comment mechanism shall be disabled. With a single non-null argument, that argument shall become the begin-comment and the shall become the end-comment string. With two non-null arguments, the first argument shall become the begin-comment string and the second argument shall become the end-comment str