Brandon Rozek

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PhD Student @ RPI studying Automated Reasoning in AI and Linux Enthusiast.

Parsing CLI Flags in Bash

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I was creating a bash script and was looking around for a solution for parsing command line arguments. This StackOverflow post has a variety of different solutions available. I want to describe my favorite of these posts.

Inanc Gumus proposed the following:


while [[ "$#" -gt 0 ]]; do case $1 in
  -d|--deploy) deploy="$2"; shift;;
  -u|--uglify) uglify=1;;
  *) echo "Unknown parameter passed: $1"; exit 1;;
esac; shift; done

echo "Should deploy? $deploy"
echo "Should uglify? $uglify"

Let me quickly describe what it does. While the number of arguments left to process is greater than zero….

  • Check to see if the argument matches any of the flags
    • If it does…
      • If the flag requires an additional argument grab it. Then discard an argument.
    • If it doesn’t. Error out.
    • Then get rid of an argument.

At the end of the while loop, you would’ve evaluated all the arguments!

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