{tag=Essays by Ciro Santilli}

Big goals:
* the pursuit of <AGI>
* <computational physics>[physics simulations], including <scientific visualization software>
* <formalization of mathematics>

Just <art>:
* useless mathy stuff
* incredibly nifty little tools that are just so satisfying to use it is mind blowing:
  * <ncdu>
  * <GNU parallel>
* media related stuff
  * <FFmpeg> one liners!


The art of programming

{tag=Good}
{tag=GNU package}
{wiki}

The author Ole Tange answers every question about it on <Stack Exchange>. What a legend!

This program makes you respect <GNU make> a bit more. Good old make with `-j` can not only parallelize, but also take in account a <dependency graph>.

Some examples under:
``
man parallel_exampes
``

To get the input argument explicitly job number use the magic string `{}`, e.g.:
``
printf 'a\nb\nc\n' | parallel echo '{}'
``
sample output:
``
a
b
c
``

To get the job number use `{#}` as in:
``
printf 'a\nb\nc\n' | parallel echo '{} {#}'
``
sample output:
``
a 1
b 2
c 3
c 3
``

`{%}` contains which thread the job running in, e.g. if we limit it to `2` threads with `-j2`:
``
printf 'a\nb\nc\nd\n' | parallel -j2 echo '{} {#} {%}'
``
sample output:
``
a 1 1
b 2 1
c 3 2
d 4 1
``
The percent must be a reference to "split the inputs module the number of workers", and modulo uses the `%` symbol in many programming languages such as <C (language)>.

To pass multiple CLI arguments per command you can use `-X` e.g.:
``
printf 'a\nb\nc\nd\n' | parallel -j2 -X echo '{} {#} {%}'
``
sample output:
``
a b 1 1
c d 2 2
``


Ciro Santilli @cirosantilli 37

 Incoming links: GNU parallel