Command Line

Open a port for a single MAC address

$ sudo ufw enable
$ sudo /sbin/iptables -A INPUT -p tcp --destination-port <port> -m mac --mac-source <mac_address> -j ACCEPT

find

$ find . -iname "*match*" -exec rm -r {} +
  • {} is replaced by all matches at once.
  • + is a terminator, but is also used to denote this style of interpolation.
$ find . -iname "*match*" -exec rm -r {} \;
  • {} is replaced by matches one at a time.
  • - is a terminator, but is also used to denote this style of interpolation.

xargs

# Basic usage
$ ls *.mp4 | xargs -n1 -P4 command

# Positional
$ ls *.mp4 xargs -I{} -n1 -P4 command {} out.xyz

GNU Parallel

https://www.gnu.org/software/parallel/

This has a bit of a learning curve, but gives you more control than xargs -P.

Run copies of a program without any arguments

$ parallel -n0 program program_args ::: {1..10}
$ seq 10 | parallel -n0 program program_args

Run named copies of a program, with labelled output

The “name” is passed as the final argument to the program. I can’t find a way to keep names around for --tag without passing them to the program; -n0 appears to print empty tags, unfortunately.

$ parallel --tag program program_args ::: {1..10}
$ seq 10 | parallel --tag program program_args

Enable line-buffering

As far as I can tell, default behavior is to buffer internally and only flush to STDOUT when a program is done. The --lb flag enables line buffering, so a flush occurs on every newline.

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