Shell Tricks: Pretty Printing the name of your program

You might need to print or use the name of your program itself --- what you would see if you ran basename my-script.sh. tl;dr: use ${0##*/}.

This is the same thing as basename, but, it is faster since you don’t have to shell out.

To expand on this, first, why would you need the name of your program? Usually this is for help text, error output, or interactive prompts. I most commonly use it for errors.

Suppose I had a /usr/local/bin/mmm-bacon script:

#!/usr/bin/env bash
 
if [[ -f ~/.config/bacon.json ]]; then
  echo "${0##*/}: Error, no bacon!"
  exit 1
fi

Here, ${0##*/} outputs mmm-bacon.

Breaking down the syntax:

• $0 refers to the full path of the script running, which would be /usr/local/bin/mmm-bacon in the example
• ${ } is a way to use parameter expansion
• ## says replace from the start of the string to the last match
• */ match against any character, followed by a /

Or, in English: strip everything from the start of the script path to the last / character.