make - GNU make utility to maintain groups of programs


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


   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 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
   very 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:


   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 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

   -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 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.

        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.  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 argument, 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

   -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

   -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 collected 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 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
        ``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 make where -k might be inherited from the
        top-level make via MAKEFLAGS or if you set -k in MAKEFLAGS in your

   -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

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

   -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.

        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 when an undefined variable is referenced.


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


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

          info make

   should give you access to the complete manual.


   Using  the  -j  option,  the user can instruct make to execute tasks in
   parallel. By specifying 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.


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


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


   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


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