MAKE(1)                                   User Commands                                   MAKE(1)

NAME
       make - GNU make utility to maintain groups of programs

SYNOPSIS
       make [OPTION]... [TARGET]...

DESCRIPTION
       The  make  utility will determine automatically which pieces of a large program need to be
       recompiled, and issue the commands to recompile them.  The manual describes the GNU imple‐
       mentation  of  make, which was written by Richard Stallman and Roland McGrath, and is cur‐
       rently maintained by Paul Smith.  Our examples show C programs, since they are  very  com‐
       mon,  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 rela‐
       tionships 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
       description 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 makefile.

       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 GNU‐
       makefile, makefile, and Makefile, in that order.

       Normally you should call your makefile either makefile or Makefile.  (We  recommend  Make‐
       file  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 recom‐
       mended  for  most makefiles.  You should use this name if you have a makefile that is spe‐
       cific 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.

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 mul‐
            tiple  -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 informa‐
            tion 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.

       --debug[=FLAGS]
            Print debugging information in addition to normal processing.  If the FLAGS are omit‐
            ted, 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.  Use n to disable all previous debugging
            flags.

       -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 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 argu‐
            ment, make will not limit the number of jobs that can run simultaneously.  When  make
            invokes a sub-make, all instances of make will coordinate to run the specified number
            of jobs at a time; see the section PARALLEL MAKE AND THE JOBSERVER for details.

       --jobserver-fds [R,W]
            Internal option make uses to pass the jobserver pipe read and write  file  descriptor
            numbers to sub-makes; see the section PARALLEL MAKE AND THE JOBSERVER for details

       -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 run‐
            ning and the load average is at least load (a floating-point number).  With no  argu‐
            ment, 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.

       -O[type], --output-sync[=type]
            When running multiple jobs in parallel with -j, ensure the output of each job is col‐
            lected together rather than interspersed with output from other jobs.  If type is not
            specified or is target the output from the entire recipe for each target  is  grouped
            together.   If  type  is  line  the  output from each command line within a recipe is
            grouped together.  If type is recurse output from an entire recursive make is grouped
            together.  If type is none output synchronization is disabled.

       -p, --print-data-base
            Print  the  data base (rules and variable values) that results from reading the make‐
            files; 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 try‐
            ing 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 other‐
            wise.

       -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.

       --trace
            Information  about the disposition of each target is printed (why the target is being
            rebuilt and what commands are run to rebuild it).

       -v, --version
            Print the version of the make 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  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 tar‐
       gets 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.

SEE ALSO
       The  full  documentation for make is maintained as a Texinfo manual.  If the info and make
       programs are properly installed at your site, the command

              info make

       should give you access to the complete manual.

PARALLEL MAKE AND THE JOBSERVER
       Using the -j option, the user can instruct make to execute tasks in parallel. By  specify‐
       ing a numeric argument to -j the user may specify an upper limit of the number of parallel
       tasks to be run.

       When the build environment is such that a top level make invokes sub-makes (for  instance,
       a style in which each sub-directory contains its own Makefile ), no individual instance of
       make knows how many tasks are running in parallel, so keeping the number  of  tasks  under
       the  upper  limit would be impossible without communication between all the make instances
       running. While solutions like having the top level make serve as a central controller  are
       feasible,  or  using other synchronization mechanisms like shared memory or sockets can be
       created, the current implementation uses a simple shared pipe.

       This pipe is created by the top-level make process, and passed on to  all  the  sub-makes.
       The  top  level makeprocesswrites N-1 one-byte tokens into the pipe (The top level make is
       assumed to reserve one token for itself). Whenever any of the  make  processes  (including
       the  top-level  make  )  needs to run a new task, it reads a byte from the shared pipe. If
       there are no tokens left, it must wait for a token to be written back to  the  pipe.  Once
       the  task is completed, the make process writes a token back to the pipe (and thus, if the
       tokens had been exhausted, unblocking the first make process that was waiting  to  read  a
       token).   Since  only  N-1  tokens were written into the pipe, no more than N tasks can be
       running at any given time.

       If the job to be run is not a sub-make then  make  will  close  the  jobserver  pipe  file
       descriptors  before  invoking the commands, so that the command can not interfere with the
       jobserver, and the command does not find any unusual file descriptors.

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

AUTHOR
       This manual page contributed by Dennis Morse of Stanford University.  Further updates con‐
       tributed  by  Mike Frysinger.  It has been reworked by Roland McGrath.  Maintained by Paul
       Smith.

COPYRIGHT
       Copyright © 1992-1993, 1996-2014 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/.

GNU                                       03 March 2012                                   MAKE(1)

Usage: make [options] [target] ...
Options:
  -b, -m                      Ignored for compatibility.
  -B, --always-make           Unconditionally make all targets.
  -C DIRECTORY, --directory=DIRECTORY
                              Change to DIRECTORY before doing anything.
  -d                          Print lots of debugging information.
  --debug[=FLAGS]             Print various types of debugging information.
  -e, --environment-overrides
                              Environment variables override makefiles.
  --eval=STRING               Evaluate STRING as a makefile statement.
  -f FILE, --file=FILE, --makefile=FILE
                              Read FILE as a makefile.
  -h, --help                  Print this message and exit.
  -i, --ignore-errors         Ignore errors from recipes.
  -I DIRECTORY, --include-dir=DIRECTORY
                              Search DIRECTORY for included makefiles.
  -j [N], --jobs[=N]          Allow N jobs at once; infinite jobs with no arg.
  -k, --keep-going            Keep going when some targets can't be made.
  -l [N], --load-average[=N], --max-load[=N]
                              Don't start multiple jobs unless load is below N.
  -L, --check-symlink-times   Use the latest mtime between symlinks and target.
  -n, --just-print, --dry-run, --recon
                              Don't actually run any recipe; just print them.
  -o FILE, --old-file=FILE, --assume-old=FILE
                              Consider FILE to be very old and don't remake it.
  -O[TYPE], --output-sync[=TYPE]
                              Synchronize output of parallel jobs by TYPE.
  -p, --print-data-base       Print make's internal database.
  -q, --question              Run no recipe; exit status says if up to date.
  -r, --no-builtin-rules      Disable the built-in implicit rules.
  -R, --no-builtin-variables  Disable the built-in variable settings.
  -s, --silent, --quiet       Don't echo recipes.
  -S, --no-keep-going, --stop
                              Turns off -k.
  -t, --touch                 Touch targets instead of remaking them.
  --trace                     Print tracing information.
  -v, --version               Print the version number of make and exit.
  -w, --print-directory       Print the current directory.
  --no-print-directory        Turn off -w, even if it was turned on implicitly.
  -W FILE, --what-if=FILE, --new-file=FILE, --assume-new=FILE
                              Consider FILE to be infinitely new.
  --warn-undefined-variables  Warn when an undefined variable is referenced.

This program built for x86_64-pc-linux-gnu
Report bugs to <bug-make (kukac) gnu.org>