The m4 macro processor

M4 is a macro processor available on UNIX† andGCOS. Its primary use has been as a front end for Ratfor for those cases where parameterless macros are not adequately powerful. It has also been used for languages as disparate as C and Cobol. M4 is particularly suited for functional languages like Fortran, PL/I and C since macros are specified in a functional notation. M4 provides features seldom found even in much larger macro processors, including •arguments •condition testing •arithmetic capabilities •string and substring functions •file manipulation This paper is a user’s manual for M4.