Unix Shell - The select Loop

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The select loop provides an easy way to create a numbered menu from which users can select options. It is useful when you need to ask the user to choose one or more items from a list of choices.

Syntax:

select var in word1 word2 ... wordN
do
   Statement(s) to be executed for every word.
done

Here var is the name of a variable and word1 to wordN are sequences of characters separated by spaces (words). Each time the for loop executes, the value of the variable var is set to the next word in the list of words, word1 to wordN.

For every selection a set of commands would be executed with-in the loop. This loop was introduced in ksh and has been adapted into bash. It is not available in sh.

Example:

Here is a simple example to let the user select a drink of choice:

#!/bin/ksh

select DRINK in tea cofee water juice appe all none
do
   case $DRINK in
      tea|cofee|water|all) 
         echo "Go to canteen"
         ;;
      juice|appe)
         echo "Available at home"
      ;;
      none) 
         break 
      ;;
      *) echo "ERROR: Invalid selection" 
      ;;
   esac
done

The menu presented by the select loop looks like the following:

$./test.sh
1) tea
2) cofee
3) water
4) juice
5) appe
6) all
7) none
#? juice
Available at home
#? none
$

You can change the prompt displayed by the select loop by altering the variable PS3 as follows:

$PS3="Please make a selection => " ; export PS3
$./test.sh
1) tea
2) cofee
3) water
4) juice
5) appe
6) all
7) none
Please make a selection => juice
Available at home
Please make a selection => none
$


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