Part 1: GNU Parallel script processing and execution

If you use xargs today you will find GNU parallel very easy to use as GNU parallel is written to have the same options as xargs. If you write loops in shell, you will find GNU parallel may be able to replace most of the loops and make them run faster by running several jobs in parallel. If you use ppss or pexec you will find GNU parallel will often make the command easier to read.

GNU parallel makes sure output from the commands is the same output as you would get had you run the commands sequentially. This makes it possible to use output from GNU parallel as input for other programs.

For each line of input GNU parallel will execute command with the line as arguments. If no command is given, the line of input is executed. Several lines will be run in parallel. GNU parallel can often be used as a substitute for xargs or cat | bash.

[paulhancock]

How do I play all these videos at the same time?

[HumanSpeak]

Yesterday, I started to convert my scripts to use parallel -- it is a great tool and so far conversion is smooth. Thank you very much!

[forric]

Hi Five from 2021 - wish I heard about parallel before now lol - I appreciate your video!

[technicalsupport-eock]

Thank you for creating what looks like an excellent tool, and for providing a fantastic tutorial. I'm looking forward to trying it out.

[Stephanbitterwolf]

Thank you for this great explanation! And you know... for making the whole tool.

[jeremyrebelka]

this thing is amazing - I'm using it for video transcoding - it compiles no problem even on old systems it is very small yet extremely useful

[odoublewen]

GNU parallel.... the best thing since sliced bread.

[leadrevolver]

A man page for a GNU utility that links to youtube?
what sort of craziness is this?

[bmjpdx]

When you're running benchmarks ('time') of something that has to read files, be aware that the first run may be constrained by filesystem I/O. But that will get the files being read into the filesystem cache (RAM, or, as we used to say, core :-), and subsequent runs will be *much* faster reading from memory rather than disk (even with SSD). User CPU consumption won't change much, but wall-clock time will be dramatically reduced.
(And if the app is _writing_ to disk, it may finish before all physical writing is complete. (The 'sync' command will wait for that to be done.))

[Xzqx]

This is the first youtube video I've found linked from a man page. I wanted it to be Rick Astley SO BAD -- was almost disappointed when it wasn't.

[murpholinox]

Very nice explained. I am learning a lot!

[felipecaetano]

Thanks a lot bro. Ive been trying this for 5 hours!

[lonegroover]

Outstanding. Will be plumbing this into my MP3 conversion script today.

[BecomingOffgrid]

Parallel is sick, what an amazing tool. I would like to see parallel in the upstream linux kernel

[mikevandewege]

This my new favorite bash function...thank you, thank you, thank you....thank you!

[OleTange]

@thomasknauth the {}, {.}, {3}, and {3.} are all GNU Parallel specific. It is not dependent on the shell.

[fotmasta]

This is the greatest thing! Deep feature set. Unfortunately for my peanut brain, there are more than a few ways to approach a problem with this. Lots of A-B-C comparisons. 

[hathuctube]

Ole' !
Great tool!. Isn't this what the openCL folks tried to accomplish?
Thanks!

[zipper-j]

Looks like a possibly very useful tool. Can't wait to run across a real problem to use it on.

[brdn]

kick-ass. i would pay that 10, 000 if i had it -- this is gold