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make - GNU make utility to maintain groups of programs
make
[ -f makefile ] [ option ] ... target ...
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.texinfo. This man page may only display a partial list of options. For
the full list, please refer to the Info manual referred to above.
The
purpose of the make 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. 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-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.
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 modified, or if the target
does not exist.
- -b
- -m
- These options are ignored for compatibility with
other versions of make.
- -C 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 interesting
about how make decides what to do.
- -e
- Give variables taken from the environment
precedence over variables from makefiles.
- -f file
- Use file as a makefile.
- -i
- Ignore all errors in commands executed to remake files.
- -I 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 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
- 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
- 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
- -l 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.
- -n
- Print the commands that would be executed, but do not execute them.
- -o
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 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 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
- Eliminate use of the built-in implicit rules. Also clear out the default
list of suffixes for suffix rules.
- -s
- Silent operation; do not print the
commands as they are executed.
- -S
- 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 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
- Print
the version of the make program plus a copyright, a list of authors and
a notice that there is no warranty.
- -w
- 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.
- -W 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.
The GNU Make Manual
See the chapter ‘Problems
and Bugs’ in The GNU Make Manual .
This manual page contributed by
Dennis Morse of Stanford University. It has been reworked by Roland McGrath.
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