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make - GNU make utility to maintain groups of programs
make [ -f makefile ] [ options ] ... [ targets ] ...
WARNING
This man page is an extract of the documentation of GNU make. It is updated only occasionally, because the GNU
project does not use nroff. For complete, current documentation, refer to the Info file make.info which is made
from the Texinfo source file make.texi.
DESCRIPTION
The purpose of the make utility is to determine automatically which pieces of a large program need to be recom-
piled, and issue the commands to recompile them. The manual describes the GNU implementation of make, which was
written by Richard Stallman and Roland McGrath, and is currently maintained by Paul Smith. Our examples show C
programs, since they are most common, but you can use make with any programming language whose compiler can be
run with a shell command. In fact, make is not limited to programs. You can use it to describe any task where
some files must be updated automatically from others whenever the others change.
To prepare to use make, you must write a file called the makefile that describes the relationships among files in
your program, and the states the commands for updating each file. In a program, typically the executable file is
updated from object files, which are in turn made by compiling source files.
Once a suitable makefile exists, each time you change some source files, this simple shell command:
make
suffices to perform all necessary recompilations. The make program uses the makefile data base and the last-mod-
ification times of the files to decide which of the files need to be updated. For each of those files, it issues
the commands recorded in the data base.
make executes commands in the makefile to update one or more target names, where name is typically a program. If
no -f option is present, make will look for the makefiles GNUmakefile, makefile, and Makefile, in that order.
Normally you should call your makefile either makefile or Makefile. (We recommend Makefile because it appears
prominently near the beginning of a directory listing, right near other important files such as README.) The
first name checked, GNUmakefile, is not recommended for most makefiles. You should use this name if you have a
makefile that is specific to GNU make, and will not be understood by other versions of make. If makefile is `-',
the standard input is read.
make updates a target if it depends on prerequisite files that have been modified since the target was last modi-
fied, or if the target does not exist.
OPTIONS
-b, -m
These options are ignored for compatibility with other versions of make.
-B, --always-make
Unconditionally make all targets.
-C dir, --directory=dir
Change to directory dir before reading the makefiles or doing anything else. If multiple -C options are
specified, each is interpreted relative to the previous one: -C / -C etc is equivalent to -C /etc. This is
typically used with recursive invocations of make.
-d Print debugging information in addition to normal processing. The debugging information says which files
are being considered for remaking, which file-times are being compared and with what results, which files
actually need to be remade, which implicit rules are considered and which are applied---everything interest-
ing about how make decides what to do.
--debug[=FLAGS]
Print debugging information in addition to normal processing. If the FLAGS are omitted, then the behavior
is the same as if -d was specified. FLAGS may be a for all debugging output (same as using -d), b for basic
debugging, v for more verbose basic debugging, i for showing implicit rules, j for details on invocation of
commands, and m for debugging while remaking makefiles.
-e, --environment-overrides
Give variables taken from the environment precedence over variables from makefiles.
+-f file, --file=file, --makefile=FILE
Use file as a makefile.
-i, --ignore-errors
Ignore all errors in commands executed to remake files.
-I dir, --include-dir=dir
Specifies a directory dir to search for included makefiles. If several -I options are used to specify sev-
eral directories, the directories are searched in the order specified. Unlike the arguments to other flags
of make, directories given with -I flags may come directly after the flag: -Idir is allowed, as well as -I
dir. This syntax is allowed for compatibility with the C preprocessor's -I flag.
-j [jobs], --jobs[=jobs]
Specifies the number of jobs (commands) to run simultaneously. If there is more than one -j option, the
last one is effective. If the -j option is given without an argument, make will not limit the number of
jobs that can run simultaneously.
-k, --keep-going
Continue as much as possible after an error. While the target that failed, and those that depend on it,
cannot be remade, the other dependencies of these targets can be processed all the same.
-l [load], --load-average[=load]
Specifies that no new jobs (commands) should be started if there are others jobs running and the load aver-
age is at least load (a floating-point number). With no argument, removes a previous load limit.
-L, --check-symlink-times
Use the latest mtime between symlinks and target.
-n, --just-print, --dry-run, --recon
Print the commands that would be executed, but do not execute them.
-o file, --old-file=file, --assume-old=file
Do not remake the file file even if it is older than its dependencies, and do not remake anything on account
of changes in file. Essentially the file is treated as very old and its rules are ignored.
-p, --print-data-base
Print the data base (rules and variable values) that results from reading the makefiles; then execute as
usual or as otherwise specified. This also prints the version information given by the -v switch (see
below). To print the data base without trying to remake any files, use make -p -f/dev/null.
-q, --question
``Question mode. Do not run any commands, or print anything; just return an exit status that is zero if
the specified targets are already up to date, nonzero otherwise.
-r, --no-builtin-rules
Eliminate use of the built-in implicit rules. Also clear out the default list of suffixes for suffix rules.
-R, --no-builtin-variables
Don't define any built-in variables.
-s, --silent, --quiet
Silent operation; do not print the commands as they are executed.
-S, --no-keep-going, --stop
Cancel the effect of the -k option. This is never necessary except in a recursive make where -k might be
inherited from the top-level make via MAKEFLAGS or if you set -k in MAKEFLAGS in your environment.
-t, --touch
Touch files (mark them up to date without really changing them) instead of running their commands. This is
used to pretend that the commands were done, in order to fool future invocations of make.
-v, --version
Print the version of the make program plus a copyright, a list of authors and a notice that there is no war-
ranty.
-w, --print-directory
Print a message containing the working directory before and after other processing. This may be useful for
tracking down errors from complicated nests of recursive make commands.
--no-print-directory
Turn off -w, even if it was turned on implicitly.
-W file, --what-if=file, --new-file=file, --assume-new=file
Pretend that the target file has just been modified. When used with the -n flag, this shows you what would
happen if you were to modify that file. Without -n, it is almost the same as running a touch command on the
given file before running make, except that the modification time is changed only in the imagination of
make.
--warn-undefined-variables
Warn when an undefined variable is referenced.
EXIT STATUS
GNU make exits with a status of zero if all makefiles were successfully parsed and no targets that were built
failed. A status of one will be returned if the -q flag was used and make determines that a target needs to be
rebuilt. A status of two will be returned if any errors were encountered.
RELATED
The GNU Make Manual
BUGS
See the chapter `Problems and Bugs' in The GNU Make Manual.
COPYRIGHT
Copyright (C) 1992, 1993, 1996, 1999 Free Software Foundation, Inc. This file is part of GNU make.
GNU make is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either version 2, or (at your option) any later version.
GNU make is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public License along with GNU make; see the file COPYING. If
not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
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