How can you use the `-a` option of `which` command to discover all installations of a command?

Hello! You can use the -a option with the which command by simply adding it before the command you want to search for. For example, to find all installations of python, you would type:

which -a python

The -a option tells which to print all matching executables found in your system's PATH, rather than stopping after the first one it finds. This is very useful when you suspect there might be multiple versions of a command installed on your system.

Let me know if you have any more questions!