'\" t
.\"     Title: parallel
.\"    Author: Joey Hess
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 2009-07-02
.\"    Manual: moreutils
.\"    Source: moreutils
.\"  Language: English
.\"
.TH "PARALLEL" "1" "2009\-07\-02" "moreutils" "moreutils"
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.SH "NAME"
parallel \- run programs in parallel
.SH "SYNOPSIS"
.HP \w'\fBparallel\fR\fB\-\-\fR\ 'u
\fBparallel\fR [options] [command]\fB\-\-\fR [argument\ \&.\&.\&.]
.HP \w'\fBparallel\fR\fB\-\-\fR\ 'u
\fBparallel\fR [options]\fB\-\-\fR [command\ \&.\&.\&.]
.SH "DESCRIPTION"
.PP
\fBparallel\fR
runs the specified command, passing it a single one of the specified arguments\&. This is repeated for each argument\&. Jobs may be run in parallel\&. The default is to run one job per CPU\&.
.PP
If no command is specified before the \-\-, the commands after it are instead run in parallel\&.
.SH "OPTIONS"
.PP
\fB\-j maxjobs\fR
.RS 4
Use to limit the number of jobs that are run at the same time\&.
.RE
.PP
\fB\-l maxload\fR
.RS 4
Wait as needed to avoid starting new jobs when the system\*(Aqs load average is not below the specified limit\&.
.RE
.PP
\fB\-i\fR
.RS 4
Normally the command is passed the argument at the end of its command line\&. With this option, any instances of "{}" in the command are replaced with the argument\&.
.RE
.PP
\fB\-n\fR
.RS 4
Number of arguments to pass to a command at a time\&. Default is 1\&. Incompatible with \-i
.RE
.SH "EXAMPLE"
.PP
\fBparallel sh \-c "echo hi; sleep 2; echo bye" \-\- 1 2 3\fR
.PP
This runs three subshells that each print a message, delay, and print another message\&. If your system has multiple CPUs, parallel will run some of the jobs in parallel, which should be clear from the order the messages are output\&.
.PP
\fBparallel \-j 3 ufraw \-o processed \-\- *\&.NEF\fR
.PP
This runs three ufraw processes at the same time until all of the NEF files have been processed\&.
.PP
\fBparallel \-j 3 \-\- ls df "echo hi"\fR
.PP
This runs three independent commands in parallel\&.
.SH "EXIT STATUS"
.PP
Its exit status is the combination of the exit statuses of each command ran, ORed together\&. (Thus, if any one command exits nonzero,
\fBparallel\fR
as a whole will exit nonzero\&.)
.SH "NOTES"
.PP
All output to stdout and stderr is serialised through a corresponding internal pipe, in order to prevent annoying concurrent output behaviour\&. Note that serialisation is not done on any other file descriptors and file position based access to a nonstandard file descriptor might have unexpected results\&.
.SH "AUTHOR"
.PP
Tollef Fog Heen