Using a variable as a case pattern in Bash

Question

I'm trying to write a Bash script that uses a variable as a pattern in a case statement. However, I just cannot get it to work.

Case statement:

case "$1" in
    $test)
        echo "matched"
        ;;
    *)
        echo "didn't match"
        ;;
esac

I've tried this with assigning $test as aaa|bbb|ccc, (aaa|bbb|ccc), [aaa,bbb,ccc] and several other combinations. I also tried these as the pattern in the case statement: @($test), @($(echo $test)), $($test). Also no success.

For clarity, I would like the variable to represent multiple patterns like this:

case "$1" in
    aaa|bbb|ccc)
        echo "matched"
        ;;
    *)
        echo "didn't match"
        ;;
esac

Answer 1

Here's something a bit different:

#!/bin/bash

pattern1="aaa bbb ccc"
pattern2="hello world"
test=$(echo -e "$pattern1\n$pattern2" | grep -e $1)

case "$test" in
    "$pattern1")
        echo "matched - pattern1"
        ;;
    "$pattern2")
        echo "matched - pattern2"
        ;;
    *)
        echo "didn't match"
        ;;
esac

This makes use of grep to do the pattern matching for you, but still allows you to specify multiple pattern sets to be used in a case-statement structure.

For instance:

• If either aaa, bbb, or ccc is the first argument to the script, this will output matched - pattern1.
• If either hello or world is the first argument, this will output matched - pattern2.
• Otherwise it will output didn't match.

Answer 2

Using eval also works:

eval 'case "$1" in

    '$test')
        echo "matched"
        ;;
    *)
        echo "did not match"
        ;;
esac'