GMAKE(1L)

NAME
gmake - GNU make utility to maintain groups of programs

SYNOPSIS
gmake [ -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 gmake utility is to determine automatically which pieces of a large program need to be recompiled, 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 gmake with any programming language whose compiler can be run with a shell command. In fact, gmake 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 gmake, 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:

    gmake

suffices to perform all necessary recompilations. The gmake program uses the makefile data base and the last-modification 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.

gmake executes commands in the makefile to update one or more target names, where name is typically a program. If no -f option is present, gmake 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.

gmake updates a target if it depends on prerequisite files that have been modified since the target was last modified, 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 gmake.

-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 interesting about how gmake 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 several directories, the directories are searched in the order specified. Unlike the arguments to other flags of gmake, 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, gmake 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 average 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 (except in certain circumstances).

-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 gmake -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 gmake where -k might be inherited from the top-level gmake 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 gmake.

-v, --version
    Print the version of the gmake program plus a copyright, a list of authors and a notice that there is no warranty.

-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 gmake 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 gmake, except that the modification time is changed only in the imagination of gmake.

--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 gmake determines that a target needs to be rebuilt. A status of two will be returned if any errors were encountered.

SEE ALSO
The GNU Make Manual

BUGS
See the chapter `Problems and Bugs' in The GNU Make Manual.

AUTHOR
This manual page contributed by Dennis Morse of Stanford University. It has been reworked by Roland McGrath. Further updates contributed by Mike Frysinger.

COPYRIGHT
Copyright (C) 1992, 1993, 1996, 1999, 2007 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 3 of the License, 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 this program. If not, see http://www.gnu.org/licenses/.