What is the concept of M4 in linux

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M4 in linux is a macro processor that can copy input to output and expand macros, which can be embedded or user-defined; M4 is part of the POSIX standard and can be used under all versions of Unix, so it can be used for reference files, text editing and word processing in linux.

The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

What is M4 in linux

M4 is a general-purpose macro processor designed by Brian Collehan and Dennis Ritchie. M4 is based on the m3 macro processor extension that Ritchie developed earlier for AP-3 minicomputers.

M4 is part of the POSIX standard and is available under all versions of UNIX. Although the language can be used alone, most people need M4 simply because the "configure" script in GNU autoconf depends on it.

A macro processor (or preprocessor) is generally used as a text replacement tool. End users often use it to deal with text templates to be used repeatedly, typically for programming tools, as well as for text editing and word processing tools.

M 4 is a macro processor. Copy the input to the output while expanding the macro. Macros can be embedded or user-defined. In addition to expanding macros, M4 also has some built-in functions to reference files and execute Unix

M4 provides the following features:

Syntax is free in form, not line-based syntax

High macro expansion (macro parameters are extended in both scanning and interpolation)

Text substitution

Parameter replacement

The file contains

String operation

Conditional judgment

Mathematical operation

System interface

Programmer diagnosis

Independent of computer programming language

Independent of natural language

Programmable

Unlike most previous macro processors, M4 is not intended for any computer language or natural language; but historically, it was originally developed to support Fortran's dialect Ratfor. In addition, M4 is a complete programming language for Turing.

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