I want to check if [[ $var == foo || $var == bar || $var == more ]] without repeating $var n times.
Here's a portable solution:
case $var in foo|bar|more) ... ;; esac
And here's one that uses =~ (which requires bash 3.0 or higher):
regex='^(foo|bar|more)$' if [[ $var =~ $regex ]]; then ... fi
This one only works in bash 3.1, not in bash 3.2 (and is untested in 3.0):
if [[ $var =~ '^(foo|bar|more)$' ]]; then ... fi
Normally I would never advocate sticking code into a variable and attempting to use it -- lots of people have enormous trouble because they try to do that. In the case of =~, though, it seems to be required. Personally, I'd just stick with the case. --GreyCat