M4(1)

NAME
m4 - macro processor

SYNOPSIS
m4 [OPTION]... [FILE]...

DESCRIPTION
Process macros in FILEs. If no FILE or if FILE is `-', standard input is read.

Mandatory or optional arguments to long options are mandatory or optional for short options too.

  Operation modes:

--help
    display this help and exit

--version
    output version information and exit

-E, --fatal-warnings
    once: warnings become errors, twice: stop execution at first error

-i, --interactive
    unbuffer output, ignore interrupts

-P, --prefix-builtins
    force a `m4_' prefix to all builtins

-Q, --quiet, --silent
    suppress some warnings for builtins

--warn-macro-sequence[=REGEXP]
    warn if macro definition matches REGEXP,

    default \$\({[^}]*}\|[0-9][0-9]+\)

-W, --word-regexp=REGEXP
    use REGEXP for macro name syntax

  Preprocessor features:

-D, --define=NAME[=VALUE]
    define NAME as having VALUE, or empty

-I, --include=DIRECTORY
    append DIRECTORY to include path

-s, --synclines
    generate `#line NUM "FILE"' lines

-U, --undefine=NAME
    undefine NAME

  Limits control:

-g, --gnu
    override -G to re-enable GNU extensions

-G, --traditional
    suppress all GNU extensions

-H, --hashsize=PRIME
    set symbol lookup hash table size [65537]

-L, --nesting-limit=NUMBER
    change nesting limit, 0 for unlimited [0]

  Frozen state files:

-F, --freeze-state=FILE
    produce a frozen state on FILE at end

-R, --reload-state=FILE
    reload a frozen state from FILE at start

  Debugging:

-d, --debug[=FLAGS]
    set debug level (no FLAGS implies `aeq')

--debugfile[=FILE]
    redirect debug and trace output to FILE (default stderr, discard if empty string)

-l, --arglength=NUM
    restrict macro tracing size

-t, --trace=NAME
    trace NAME when it is defined

  FLAGS is any of:

a   show actual arguments

c   show before collect, after collect and after call

e   show expansion

f   say current input file name

i   show changes in input files

l   say current input line number

p   show results of path searches

q   quote values as necessary, with a or e flag

t   trace for all macro calls, not only traceon'ed

x   add a unique macro call id, useful with c flag

V   shorthand for all of the above flags

If defined, the environment variable `M4PATH' is a colon-separated list of directories included after any specified by `-I'.

Exit status is 0 for success, 1 for failure, 63 for frozen file version mismatch, or whatever value was passed to the m4exit macro.

AUTHOR
Written by Rene' Seindal.

REPORTING BUGS
Report bugs to: bug-m4@gnu.org
GNU M4 home page: <https://www.gnu.org/software/m4/>
General help using GNU software: <https://www.gnu.org/gethelp/>

COPYRIGHT
Copyright © 2026 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

SEE ALSO
The full documentation for m4 is maintained as a Texinfo manual. If the info and m4 programs are properly installed at your site, the command

    info m4

should give you access to the complete manual.