|command||Command to execute. The command may be followed by arguments for the command.|
Run command in background thus GNU sem will not wait for
completion of the command before exiting. This is the default.
In toilet analogy: GNU sem waits for a toilet to be available, gives the toilet to a person, and exits immediately.
See also: --fg
Run up to N commands in parallel. Default is 1 thus acting like a
In toilet analogy: -j is the number of toilets.
|-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.|
|-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.|
|-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.|
|-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.|
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/
In toilet analogy the name corresponds to different types of toilets: e.g. male, female, customer, staff.
Do not put command in background.
In toilet analogy: GNU sem waits for a toilet to be available, takes a person to the toilet, waits for the person to finish, and exits.
|--semaphoretimeout secs (beta testing)|
|--st secs (beta testing)||
If secs > 0: If the semaphore is not released within secs
seconds, take it anyway.
If secs < 0: If the semaphore is not released within secs seconds, exit.
In toilet analogy: secs > 0: If no toilet becomes available within secs seconds, pee on the floor. secs < 0: If no toilet becomes available within secs seconds, exit without doing anything.
Wait for all commands to complete.
In toilet analogy: Wait until all toilets are empty, then exit.
Try the following example:
sem -j 2 sleep 1;echo 1 finished; echo sem 1 exited sem -j 2 sleep 2;echo 2 finished; echo sem 2 exited sem -j 2 sleep 3;echo 3 finished; echo sem 3 exited sem -j 2 sleep 4;echo 4 finished; echo sem 4 exited sem --wait; echo sem --wait done
In toilet analogy this uses 2 toilets (-j 2). GNU sem takes 1 to a toilet, and exits immediately. While 1 is sleeping, another GNU sem takes 2 to a toilet, and exits immediately.
While 1 and 2 are sleeping, another GNU sem waits for a free toilet. When 1 finishes, a toilet becomes available, and this GNU sem stops waiting, and takes 3 to a toilet, and exits immediately.
While 2 and 3 are sleeping, another GNU sem waits for a free toilet. When 2 finishes, a toilet becomes available, and this GNU sem stops waiting, and takes 4 to a toilet, and exits immediately.
Finally another GNU sem waits for all toilets to become free.
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
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) there is a risk that two different instances of pod2html will write to the files at the same time:
# This may fail due to shared pod2htmd.tmp/pod2htmi.tmp files foo.html: pod2html foo.pod --outfile foo.html bar.html: pod2html bar.pod --outfile bar.html $ make -j foo.html bar.html
You need to protect pod2html from running twice at the same time. sem running as a mutex will make sure only one runs:
foo.html: sem --id pod2html pod2html foo.pod --outfile foo.html bar.html: sem --id pod2html pod2html bar.pod --outfile bar.html clean: foo.html bar.html sem --id pod2html --wait rm -f pod2htmd.tmp pod2htmi.tmp $ make -j foo.html bar.html clean
Report bugs to <firstname.lastname@example.org>.
Copyright (C) 2010,2011,2012,2013 Ole Tange, http://ole.tange.dk and Free Software Foundation, Inc.
Copyright (C) 2010,2011,2012,2013 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.
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GNU sem uses Perl, and the Perl modules Getopt::Long, Symbol, Fcntl.