tldr/pages/common/parallel.md

parallel

Run commands on multiple CPU cores. More information: https://www.gnu.org/software/parallel.

• Gzip several files at once, using all cores:

parallel gzip ::: {{path/to/file1 path/to/file2 ...}}

• Read arguments from stdin, run 4 jobs at once:

ls *.txt | parallel -j4 gzip

• Convert JPEG images to PNG using replacement strings:

parallel convert {} {.}.png ::: *.jpg

• Parallel xargs, cram as many args as possible onto one command:

{{args}} | parallel -X {{command}}

• Break stdin into ~1M blocks, feed each block to stdin of new command:

cat {{big_file.txt}} | parallel --pipe --block 1M {{command}}

• Run on multiple machines via SSH:

parallel -S {{machine1}},{{machine2}} {{command}} ::: {{arg1}} {{arg2}}

• Download 4 files simultaneously from a text file containing links showing progress:

parallel -j4 --bar --eta wget -q {} :::: {{path/to/links.txt}}

• Print the jobs which parallel is running in stderr:

parallel -t {{command}} ::: {{args}}