Update cheatsheets

parallel

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# 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 JPG 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}}`