bash shell gives weird result when directory exists vs not

Question

Alright, I\'ve wasted a full day on a script that was behaving very oddly. I have found out something that I can\'t explain.

ny-02-ops:~$ rm -fr roles
ny-02-ops         


        

Answer 1

The default behaviour of the shell is to expand a glob where possible, otherwise return it unchanged. There are ways to change this behaviour, however.

To expand non-matching globs to an empty string (useful for for loops which you may just want to skip if no files match, for example), use nullglob:

shopt -s nullglob

If the fact that the glob doesn't expand is considered an error, use failglob:

shopt -s failglob

Use shopt -u to unset these shell options.

Answer 2

Square brackets in a glob match one of the characters inside. If a glob with metacharacters (*, [...], etc.) matches no filenames then the glob is returned unchanged.

echo "role[sugar]"
echo "role[blerk]"