Checking if a ruby gem is installed from bash script

I need to, from a bash script, check to see if certain Ruby gems are installed .

I thought I could do something like

if ! gem list <name>; then do_stuff; fi

but testing on the command line using echo $? shows that gem list <name> returns 0 regardless of if name is actually found.

Does this mean I have to use grep to filter the output of gem list, or is there a better way I can check to see if a gem is installed?

gem list <name> -i will return the string true if the gem is installed and false otherwise. Also, the return codes are what you would expect.

For more informations, see gem help list.

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