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 [509]

-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.