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up vote 0 down vote favorite

How do I check if a variable is in [A-Z]

I want something like this: 

read var

while [ $var in [A-Z] ]
do
 #code here
done

How to achieve this?

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Is $var a single character or do you want to test that it contains only letters? –  terdon Sep 26 '13 at 16:44
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3 Answers

up vote 2 down vote

In bash, you can use a pattern on the right hand side of a == in a [[ ... ]]:

read var
LC_ALL=C # Turn off locale.
if [[ $var == [A-Z] ]] ; then
    echo yes
fi

Turning off locale might be needed if you do not want y to be in A-Z.

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up vote 0 down vote

The simple one liner would be:

re='[a-zA-Z]'; if [[ Z =~ $re ]]; then echo "Match"; else echo "No match"; fi

The full script would be:

#!/bin/bash

re='[a-zA-Z]'
read -p "Enter a char or string > " var

if [[ "$var" =~ $re ]]; then
    echo "Entered string matches."
else 
    echo "Entered string does not match";
fi
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up vote 0 down vote

If you don't want to rely on Bash's regular expressions:

remainder=$(tr -d A-Z <<<$var)
while [ ! -z $remainder ];do
    read -p "Invalid value entered. Please try again." var
    remainder=$(tr -d A-Z <<<$var)
done

I'm guessing you want to use this for input validation.

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