Easiest way to check for file extension in bash? [duplicate]

Question

I have a shell script where I need to do one command if a file is zipped (ends in .gz) and another if it is not. I'm not really sure how to approach this, here's an outline of what I'm looking for:

file=/path/name*  if [ CHECK FOR .gz ] then echo "this file is zipped" else echo "this file is not zipped" fi 

Answer 1

You can do this with a simple regex, using the =~ operator inside a [[...]] test:

if [[ $file =~ \.gz$ ]]; 

This won't give you the right answer if the extension is .tgz, if you care about that. But it's easy to fix:

if [[ $file =~ \.t?gz$ ]]; 

The absence of quotes around the regex is necessary and important. You could quote $file but there is no point.

It would probably be better to use the file utility:

$ file --mime-type something.gz something.gz: application/x-gzip 

Something like:

if file --mime-type "$file" | grep -q gzip$; then   echo "$file is gzipped" else   echo "$file is not gzipped" fi 

Answer 2

Really, the clearest and often easiest way to match patterns like this in a shell script is with case

case "$f" in *.gz | *.tgz )          # it's gzipped         ;; *)         # it's not         ;; esac