How to list installed versions of the same program I have a program called PyMOL installed multiple times on my machine. One was installed by MacPorts, one was installed through the developers distribution channel and so on. One is in /opt/local/bin, the other is in /i/have/no/clue.

I know I can use "which pymol" to see, where the one that is executed is located, but how can I get the location of the other ones with the same name?
You have the right command and just need to set the proper option:

which -a pymol will show all instances of the executable pymol located within your PATH.

For example, on my laptop I have git installed in two places:

$ which git
/usr/local/bin/git


provides what will be run when I use the command git.

$ which -a git
/usr/local/bin/git
/usr/bin/git


provides every instance of the executable in my PATH.