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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.
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. After this information
is printed, processing continues normally. To get this information without
doing anything else, use make -v -f/dev/null.
- -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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