Posts tagged parallel

gnu parallel instead of bash for loops
posted on 2016-05-24 18:15

If you happen to have to iterate over a list of files/strings/whatever, gnu parallel comes in handy after you installed it from your linux distro's package manager.

Then instead of:

for i in *; do echo "test $i"; done

You can simply do:

ls -1 | parallel echo "test "

# alternatively:
parallel echo 'test ' ::: `ls -1`

If you happen to have more complex scripts, simply double-quote the commands handed to parallel. Use {} if you happen to need a reference to the current variable.

I.e.

parallel "echo 'number {} echoed'" ::: `seq 1 10`

which gives:

number 1 echoed
number 2 echoed
number 3 echoed
number 4 echoed
number 5 echoed
number 6 echoed
number 7 echoed
number 8 echoed
number 9 echoed
number 10 echoed

At first this does not look like much, but how often have you messed up for loops? The example is rather made up, but does work better the more complex your examples become.

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