How can I do case-insensitive string comparison in Bash?

Question

My script:

echo "input yes or no"
read a
if [ $a = "yes" ] or [ $a = "Yes" ] or [ $a = "YES" ];
then
    command
else
    command
done

I have an idea that I will convert the answer (using the tr A-Z a-z command) first and after that compare with string... is that okay?

See http://stackoverflow.com/questions/2264428/converting-string-to-lower-case-in-bash-shell-scripting — stalet, Jun 17 '16 at 10:39
Dear stalet Thanks for your link I also wrote that i can convert first, but i want to know more solutions :D — , Jun 17 '16 at 10:44
This question have already been answered here: [Case Insensitive comparision of strings in Shell script](http://stackoverflow.com/questions/1728683/case-insensitive-comparision-of-strings-in-shell-script) — mik1904, Jun 17 '16 at 10:48
Check `make 1 dialog`. E.g. https://bash.cyberciti.biz/guide/A_yes/no_dialog_box — Dummy00001, Jun 17 '16 at 11:56

score 11 · Answer 1 · answered Jun 17 '16 at 10:57

11

Here is an example on how to do it without conversion in bash 4. You can use parameter expansion to inline change the value of the $a variable.

#!/bin/bash

echo "input yes or no"
read a
if [ ${a,,} = "yes" ];
then
    echo "test 1"
else
    echo "test 2"
fi

answered Jun 17 '16 at 10:57

stalet

score 8 · Answer 2 · answered Jun 17 '16 at 10:40

8

You can use shopt -s nocasematch.

Try this :

shopt -s nocasematch
echo "Input yes or no"
read a
if [[ $a == "yes" ]]
then
    echo "YES"
else
    echo "NO"
fi

From bash:

nocasematch

If set, Bash matches patterns in a case-insensitive fashion when performing matching while executing case or [[ conditional commands.

answered Jun 17 '16 at 10:40

sat

Thanks you so much, mr.sat – Jun 17 '16 at 11:02
Do you need to unset before exit the script ? Or is it set only for the current script ? – Flows Jun 17 '16 at 11:22
1

@Flows, This will set only for current script/shell. – sat Jun 17 '16 at 11:56

score 2 · Answer 3 · answered Jun 17 '16 at 12:01

You can use the dialog tool available on most systems, which can display an interactive dialog in the console:

if dialog  --title example1 --backtitle example2 --yesno "Make a choice!" 7 60
then
    echo "YES"
else
    echo "NO"
fi

Bypasses the case-sensitivity of the user input completely.

3 Answers3