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