CODEWITHSUNDEEP
bashpattern-matchingswitch-statement
siebz0r
siebz0r

Reputation: 20329

Using a variable as a case pattern in Bash

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

Upvotes: 27

Views: 18733

Answers (3)

choroba
choroba

Reputation: 241808

You can use the extglob option:

#! /bin/bash

shopt -s extglob         # enables pattern lists like @(...|...)
test='@(aaa|bbb|ccc)'

for x in aaa bbb ccc ddd ; do
    echo -n "$x "
    case "$x" in
        $test) echo Matches.
        ;;
        *) echo Does not match.
    esac
done

Upvotes: 27

mliberi
mliberi

Reputation: 29

Using eval also works:

eval 'case "$1" in

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

Upvotes: 2

sampson-chen
sampson-chen

Reputation: 47269

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.

Upvotes: 3

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