shell - Bash: limit the number of concurrent jobs?

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Answer 1

If you have GNU Parallel http://www.gnu.org/software/parallel/ installed you can do this:

parallel gzip ::: *.log

which will run one gzip per CPU core until all logfiles are gzipped.

If it is part of a larger loop you can use sem instead:

for i in *.log ; do
    echo $i Do more stuff here
    sem -j+0 gzip $i ";" echo done
done
sem --wait

It will do the same, but give you a chance to do more stuff for each file.

If GNU Parallel is not packaged for your distribution you can install GNU Parallel simply by:

$ (wget -O - pi.dk/3 || lynx -source pi.dk/3 || curl pi.dk/3/ || 
   fetch -o - http://pi.dk/3 ) > install.sh
$ sha1sum install.sh | grep 883c667e01eed62f975ad28b6d50e22a
12345678 883c667e 01eed62f 975ad28b 6d50e22a
$ md5sum install.sh | grep cc21b4c943fd03e93ae1ae49e28573c0
cc21b4c9 43fd03e9 3ae1ae49 e28573c0
$ sha512sum install.sh | grep da012ec113b49a54e705f86d51e784ebced224fdf
79945d9d 250b42a4 2067bb00 99da012e c113b49a 54e705f8 6d51e784 ebced224
fdff3f52 ca588d64 e75f6033 61bd543f d631f592 2f87ceb2 ab034149 6df84a35
$ bash install.sh

It will download, check signature, and do a personal installation if it cannot install globally.

Watch the intro videos for GNU Parallel to learn more: https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1