How to use case statement in shell script

Last updated on July 24, 2020 by Dan Nanni

In a shell script, the case statement is often useful when you want to change the control flow of a script based on the value of a variable or an expression.

The following code snippets demonstrate the case syntax in a bash shell script. Note that the default case is preceded by *).

#!/bin/bash

CMD=$1

case "$CMD" in
    'start')
        echo "start"
        ;;
    'stop'|'halt')
        echo "stop or halt"
        ;;
    *)
        echo "Usage: ${0} [start|stop|halt]"
        ;;
esac

The case statement also supports pattern matching in evaluating each case branch. For example:

#!/bin/bash

case $filename in
    *.c )
        objname=${filename%.c}.o
        gcc $filename $objname
        ;;
    *.s )
        objname=${filename%.s}.o
        as $filename $objname 
        ;;
    *.o )
        ;;
    *)
        print "error: $filename is not a source or object file."
        ;;
esac

If you find this tutorial helpful, I recommend you check out the series of bash shell scripting tutorials provided by Xmodulo.

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