Switch (Case) Statment in Bash

The case statement is useful and processes faster than an else-if ladder. Instead of checking all if-else conditions, the case statement directly select the block to execute based on an input.

Create the first program using the case statement in a shell script. The program takes input from the user and executes statements based on the input value.

#!/bin/bash

read -p "Enter your choice [yes/no]:" choice

case $choice in
     yes)
          echo "Thank you"
          echo "Your type: Yes"
          ;;
     no)
          echo "Ooops"
          echo "You type: No"
          ;;
     *)
          echo "Sorry, invalid input"
          ;;
esac

#!/bin/bash

read -p "Enter your choice [yes/no]:" choice

case $choice in

yes)

echo "Thank you"

echo "Your type: Yes"

;;

no)

echo "Ooops"

echo "You type: No"

;;

echo "Sorry, invalid input"

;;

esac

Save the above script in case1.sh and execute the script on bash shell.

chmod +x case1.sh
./case1.sh
Enter your choice [yes/no]:yes
Thank you
Your type: Yes


./case1.sh
Enter your choice [yes/no]:no
Ooops
You type: No

./case1.sh
Enter your choice [yes/no]:anything
Sorry, invalid input

Script Execution Process:

Set the execute permission on shell script.
Executed the script first time and input “yes” to choice variable. Case matches the string with available options yes). Then executed code block under yes option.
Executed the script second time and input “no” to choice variable. Case matches the string with available options no). Then executed code block under no option.
Executed the script third time and input “anything” to choice variable. Case found not matches under available options for this string. In this situation case uses wildcard *) and executed statments under it.

Multple Strings in Case Options

You can define more than one string in the matching pattern under case statement in shell scripting. Check sample script here:

#!/bin/bash

read -p "Enter your choice [yes/no]:" choice

case $choice in
     Y/y/Yes/YES/yes)
          echo "Thank you"
          echo "Your type: Yes"
          ;;
     N/n/No/NO/no)
          echo "Ooops"
          echo "You type: No"
          ;;
     *)
          echo "Sorry, invalid input"
          ;;
esac

#!/bin/bash

read -p "Enter your choice [yes/no]:" choice

case $choice in

Y/y/Yes/YES/yes)

echo "Thank you"

echo "Your type: Yes"

;;

N/n/No/NO/no)

echo "Ooops"

echo "You type: No"

;;

echo "Sorry, invalid input"

;;

esac

Patterns Matching in Case Statement

You can use wildcard characters like *,? and [] with the case statement. But still, some of the braces expansion still not work. Now, you can set shopt -s extglob to use extended pattern matching.

#!/bin/bash

read -p "Enter a string:" choice
shopt -s extglob
case $choice in
     a*)                    ### matches anything starting with "a"
          #script here
          ;;

     b?)                    ### matches any two-character string starting with "b"
          #script here
          ;;

     s[td])                 ### matches "st" or "sd"
          #script here
          ;;

     r[ao]m)                ### matches "ram" or "rom"
          #script here
          ;;

     me?(e)t)               ### matches "met" or "meet"
          #script here
          ;;

     @(a|e|i|o|u))          ### matches one vowel
          #script here
          ;;

     *)                     ### Catchall matches anything not matched above
          #script here
          ;; 
esac

#!/bin/bash

read -p "Enter a string:" choice

shopt -s extglob

case $choice in

a*) ### matches anything starting with "a"

#script here

;;

b?) ### matches any two-character string starting with "b"

#script here

;;

s[td]) ### matches "st" or "sd"

#script here

;;

r[ao]m) ### matches "ram" or "rom"

#script here

;;

me?(e)t) ### matches "met" or "meet"

#script here

;;

@(a|e|i|o|u)) ### matches one vowel

#script here

;;

*) ### Catchall matches anything not matched above

#script here

;;

esac

Save above script in a shell script and execute it with various inputs and study about its execution.

bash, case, shell script