PARALLEL(1) moreutils PARALLEL(1)NAME
parallel - run programs in parallel
SYNOPSIS
parallel [options] [command]-- [argument ...]
parallel [options]-- [command ...]
DESCRIPTION
parallel 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.
If no command is specified before the --, the commands after it are
instead run in parallel.
OPTIONS-j maxjobs
Use to limit the number of jobs that are run at the same time.
-l maxload
Wait as needed to avoid starting new jobs when the system's load
average is not below the specified limit.
-i
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.
-n
Number of arguments to pass to a command at a time. Default is 1.
Incompatible with -i
EXAMPLE
parallel sh -c "echo hi; sleep 2; echo bye" -- 1 2 3
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.
parallel -j 3 ufraw -o processed -- *.NEF
This runs three ufraw processes at the same time until all of the NEF
files have been processed.
parallel -j 3 -- ls df "echo hi"
This runs three independent commands in parallel.
EXIT STATUS
Its exit status is the combination of the exit statuses of each command
ran, ORed together. (Thus, if any one command exits nonzero, parallel
as a whole will exit nonzero.)
NOTES
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.
AUTHOR
Tollef Fog Heen
moreutils 2009-07-02 PARALLEL(1)
