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.
-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.
GNU 22 August 1989 MAKE(1L)
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