m4
macro processor
TLDR
Process file
$ m4 [input.m4]
Output to file$ m4 [input.m4] > [output.txt]
Define macro$ m4 -D [NAME=value] [input.m4]
Include directory$ m4 -I [/path/to/includes] [input.m4]
Prefix builtins$ m4 -P [input.m4]
Debug output$ m4 -d [input.m4]
SYNOPSIS
m4 [options] [files]
DESCRIPTION
m4 is a macro processor. It expands macros in text files to generate output.
The tool is used to preprocess configuration files and source code. It's part of autoconf.
PARAMETERS
FILES
Input files to process.-D NAME=VALUE
Define macro.-U NAME
Undefine macro.-I DIR
Add include path.-P
Prefix builtins with m4_.-d
Enable debug output.--help
Display help information.
CAVEATS
POSIX standard. Quoting rules can be tricky. Used by autoconf extensively.
HISTORY
m4 was developed at Bell Labs in the 1970s. The GNU version extends the original POSIX specification.