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:
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:
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.