apropos (find a command)

If you forgot the name of a command, but you roughly remember its short description, try searching for it using apropos. I was once looking for a command that reverses the lines of a text file. I entered:

apropos reverse

Try entering this on your system. It will give you a list of commands that have the keyword “reverse” in their name or short description. The command that I was looking for was tac. You can use the command whatis to display a command's short description, for example:

whatis tac

This will output the following:

tac (1) - concatenate and print files in reverse

It's a useful way of getting some quick info on a command without invoking →man.