Comparing a variable to upper and lower case letters

Question

So I want to validate a response of a user in tcsh script and that's what I have so far

set var1="temp"
    while($var1 != [yY] && $var1 != [Yy][Ee][Ss] && $var1 != [Nn] && $var1 != [Nn][Oo])
            echo "Do you want to create a backup directory ? :"
        set response=&< 
        if ($response == [yY] || $respose == [Yy][Ee][Ss]) then
            mkdir backup
            echo "Backupd directory created \n"
        else if($response == [nN] || $response == [Nn][Oo]) then
            echo "No backup directory is created \n"
        else
            echo "Please enter a valid respose ! \n"
            var1=$response
        endif 
    end

I basically want the user to either input Y,y,Yes,N,n,No and of course I also allow for a combination of small case and upper case in yes and now.

But when I run the script, it gives me an error saying [yY]: No match.

So I am guessing something is wrong when comparing $var1 to [Yy]. Basically I am validating the user input.

And cai reassign var1 like I did, var1=$response, or do I have to use set again >

Answer 1

You probably meant !~, "does not match regular expression", rather than !=, "is not equal to".

For $var =~ regexp and $var !~ regexp, the pattern on the right should not be quoted. For == and !=, you may quote the part on the right (and in fact I'd encourage this).

Since != expects a string, "[yY] was not parsed as a regular expression. Rather, the shell expanded it to "any file whose name is y or Y". And since you didn't have one, the shell complained.

This sort of thing, by the way, is why I prefer not to write scripts in tcsh, even though I use it as my interactive shell.