In Bash, how can option flag values be stored in variables?

Question

When writing Bash scripts, how can I obtain a value from the command-line when provided as part of option flags in the command line?

For example in the following:

./script --value=myText --otherValue=100

How could I store the myText and 100 values in the variables $text and $num?

Answer 1

Use getopts.

#!/bin/bash

while getopts ":a:" opt; do
  case $opt in
    a)
      echo "-a was triggered, Parameter: $OPTARG" >&2
      ;;
    \?)
      echo "Invalid option: -$OPTARG" >&2
      exit 1
      ;;
    :)
      echo "Option -$OPTARG requires an argument." >&2
      exit 1
      ;;
  esac
done

Answer 2

If case you really need to use --longoption, if you can stick with a single char option -a, stick with what spraff said. You can do the following:

#!/bin/bash
main()
{
    [[ $1 =~ "--value=(.*)" ]] && echo "First arg: $1"
    value=${BASH_REMATCH[1]}

    [[ $2 =~ "--otherValue=(.*)" ]] && echo "Second arg: $2"
    other=${BASH_REMATCH[1]}

    echo $value
    echo $other

    #doYourThing

    return 0

}

main $*

Make sure you are running bash 3.0.

$ echo $BASH_VERSION
3.00.16(1)-release

If you have bash 4.x, do not put double quotes around the regex patterns.