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I am working on a little script that plays a game. At the end, it asks "Play again? [Y/N]" and I would like the game to loop when the user inputs any word starting with 'y'.

My code:

playAgain="yes" while [[ "$playAgain" =~ ^y* ]]; do # working game loop code read -p "Play Again? (y/n): " playAgain done echo "Thank you for playing!"

at this time the game loop will execute regardless of what is in "playAgain".
Even it I initialize playAgain to "no" the game loop will still execute.
No matter what I type into the "read" call for playAgain, the game loop will execute.

I got the regex syntax from here.

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  • do you wish to repeat the loop if the user enters a string that begins with a capital Y? Commented Jun 25 at 23:31
  • You mixed 2 different pattern matching syntaxes from superuser.com/q/1056183/1089278 - foo == y* is doing a globbing comparison while foo =~ ^y.* is doing a regexp comparison. It looks like you took the =~ from an answer doing a regexp comparison but the y* from an answer doing a globbing comparison. Globbing and regexps are both used for pattern matching and they look similar but their syntax/metachars (e.g. *) have different meanings. Commented Jun 26 at 10:49

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With the =~ operator, you're using a regular expression. ^ means start of the string, but * means "the previous token repeated zero or more times". You want to say "anything repeated zero or more times" instead, which can be expressed as .* (making the whole expression ^y.*), but you don't need to match the rest of the string: ^y is enough.

[[ $playAgain =~ ^y ]]

You can use a pattern instead of a regular expression. Then, you need to match the whole string, and * has the same meaning as in path expansion.

[[ $playAgain = y* ]]

Moreover, you can use parameter expansion, extract the first character only and use direct string comparison.

[[ ${playAgain:0:1} = y ]] # ^ ^ # | | # offset | # length
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