Bash Scripting Wildcards in Conditions

Question

I wish to check for proper user input as such (pseudo code)

userInput=""

#check until user enters 'y' OR 'Y' OR 'n' OR 'N'

while [[ "$userInput" != "[yYnN]" ]] ; do

     read userInput

done

My idea is to use the [] wild card for matching but what is the proper way to accomplish this task?

Yes. Don't use double quotes around the regexp. Do surround the expression with double brackets. — Mark Plotnick, Nov 04 '13 at 01:52
@AdamLiss ...well, this one has additional problems (using `[ ]` rather than `[[ ]]`, missing whitespace between the `while` and the test command following). — Charles Duffy, Nov 04 '13 at 02:00
@theta `[` is a command, not syntax. Like other commands (and much other syntax), it needs to be separated from things that follow it with whitespace. `while [`, not `while[`. And glob matches need `[[ ]]`, not `[ ]`. — Charles Duffy, Nov 04 '13 at 02:01

Adam Liss · Accepted Answer · 2013-11-04T01:47:07.050

2

Here's one way:

while true; do
case $userInput in
  y|Y|n|N)
    break
    ;;
  *)
    # read more input
    ;;
esac
done

If you're not concerned with portability, you can use

while [[ ! $userInput =~ [yYnN] ]]; do

edited Nov 04 '13 at 01:47

answered Nov 04 '13 at 01:35

Adam Liss

If your script starts with `#!/bin/bash`, the latter is definitely legal (re: "not concerned with portability"). – Charles Duffy Nov 04 '13 at 01:59

1 Answers1