sem (1)

Name

sem - semaphore for executing shell command lines in parallel

Synopsis

sem [--fg] [--id <id>] [--timeout <secs>] [-j <num>]
[--wait] command

Description

parallel                                                   SEM(1)



NAME
     sem - semaphore for executing shell command lines in
     parallel

SYNOPSIS
     sem [--fg] [--id <id>] [--timeout <secs>] [-j <num>]
     [--wait] command

DESCRIPTION
     GNU sem is an alias for GNU parallel --semaphore.

     It works as a tool for executing shell commands in parallel.
     GNU sem acts as a counting semaphore. When GNU sem is called
     with command it will start the command in the background.
     When num number of commands are running in the background,
     GNU sem will wait for one of these to complete before
     starting another command.

     Before looking at the options you may want to check out the
     examples after the list of options. That will give you an
     idea of what GNU sem is capable of.

OPTIONS
     command  Command to execute. The command may be followed by
              arguments for the command.

     --bg     Run command in background thus GNU parallel will
              not wait for completion of the command before
              exiting. This is the default.

              See also: --fg

     -j N     Run up to N commands in parallel. Default is 1 thus
              acting like a mutex.

     --jobs N
     -j N
     --max-procs N
     -P N     Run up to N commands in parallel. Default is 1 thus
              acting like a mutex.

     --jobs +N
     -j +N
     --max-procs +N
     -P +N    Add N to the number of CPU cores.  Run up to this
              many jobs in parallel. For compute intensive jobs
              -j +0 is useful as it will run number-of-cpu-cores
              jobs simultaneously.

     --jobs -N
     -j -N
     --max-procs -N



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parallel                                                   SEM(1)



     -P -N    Subtract N from the number of CPU cores.  Run up to
              this many jobs in parallel.  If the evaluated
              number is less than 1 then 1 will be used.  See
              also --use-cpus-instead-of-cores.

     --jobs N%
     -j N%
     --max-procs N%
     -P N%    Multiply N% with the number of CPU cores.  Run up
              to this many jobs in parallel.  If the evaluated
              number is less than 1 then 1 will be used.  See
              also --use-cpus-instead-of-cores.

     --jobs procfile
     -j procfile
     --max-procs procfile
     -P procfile
              Read parameter from file. Use the content of
              procfile as parameter for -j. E.g. procfile could
              contain the string 100% or +2 or 10.

     --semaphorename name
     --id name
              Use name as the name of the semaphore. Default is
              the name of the controlling tty (output from tty).

              The default normally works as expected when used
              interactively, but when used in a script name
              should be set. $$ or my_task_name are often a good
              value.

              The semaphore is stored in ~/.parallel/semaphores/

     --fg     Do not put command in background.

     --timeout secs (not implemented)
     -t secs (not implemented)
              If the semaphore is not released within secs
              seconds, take it anyway.

     --wait
     -w       Wait for all commands to complete.

EXAMPLE: Gzipping *.log
     Run one gzip process per CPU core. Block until a CPU core
     becomes available.

       for i in *.log ; do
         echo $i
         sem -j+0 gzip $i ";" echo done
       done
       sem --wait



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parallel                                                   SEM(1)



EXAMPLE: Protecting pod2html from itself
     pod2html creates two files: pod2htmd.tmp and pod2htmi.tmp
     which it does not clean up. It uses these two files for a
     short time. But if you run multiple pod2html in parallel
     (e.g. in a Makefile with make -j) you need to protect
     pod2html from running twice at the same time. sem running as
     a mutex will do just that:

       sem --fg --id pod2html pod2html foo.pod > foo.html
       sem --fg --id pod2html rm -f pod2htmd.tmp pod2htmi.tmp

BUGS
     None known.

REPORTING BUGS
     Report bugs to <[email protected]>.

AUTHOR
     Copyright (C) 2010,2011,2012 Ole Tange, http://ole.tange.dk
     and Free Software Foundation, Inc.

LICENSE
     Copyright (C) 2010,2011,2012 Free Software Foundation, Inc.

     This program 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.

     This program 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/>.

  Documentation license I
     Permission is granted to copy, distribute and/or modify this
     documentation under the terms of the GNU Free Documentation
     License, Version 1.3 or any later version published by the
     Free Software Foundation; with no Invariant Sections, with
     no Front-Cover Texts, and with no Back-Cover Texts.  A copy
     of the license is included in the file fdl.txt.

  Documentation license II
     You are free:

     to Share to copy, distribute and transmit the work



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parallel                                                   SEM(1)



     to Remix to adapt the work

     Under the following conditions:

     Attribution
              You must attribute the work in the manner specified
              by the author or licensor (but not in any way that
              suggests that they endorse you or your use of the
              work).

     Share Alike
              If you alter, transform, or build upon this work,
              you may distribute the resulting work only under
              the same, similar or a compatible license.

     With the understanding that:

     Waiver   Any of the above conditions can be waived if you
              get permission from the copyright holder.

     Public Domain
              Where the work or any of its elements is in the
              public domain under applicable law, that status is
              in no way affected by the license.

     Other Rights
              In no way are any of the following rights affected
              by the license:

              o Your fair dealing or fair use rights, or other
                applicable copyright exceptions and limitations;

              o The author's moral rights;

              o Rights other persons may have either in the work
                itself or in how the work is used, such as
                publicity or privacy rights.

     Notice   For any reuse or distribution, you must make clear
              to others the license terms of this work.

     A copy of the full license is included in the file as
     cc-by-sa.txt.

DEPENDENCIES
     GNU sem uses Perl, and the Perl modules Getopt::Long,
     Symbol, Fcntl.


ATTRIBUTES
     See attributes(5) for descriptions of the following
     attributes:



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parallel                                                   SEM(1)



     +---------------+------------------+
     |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
     +---------------+------------------+
     |Availability   | shell/parallel   |
     +---------------+------------------+
     |Stability      | Uncommitted      |
     +---------------+------------------+
SEE ALSO
     parallel(1)



NOTES
     This software was built from source available at
     https://java.net/projects/solaris-userland.  The original
     community source was downloaded from
     http://ftp.gnu.org/gnu/parallel/parallel-20121122.tar.bz2

     Further information about this software can be found on the
     open source community website at
     http://www.gnu.org/software/parallel/.


































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