Type, which and whereis (Display Command Information)

There are several Linux commands that give you information about Linux commands besides the man command.

type – displays the type of a command

The type command returns types of commands. There are largely three types.

1. Shell built-in command (internal command)
2. External command (shell refers to the path of a command when it executes it)
3. Alias

Here are examples of the three types.

type echo

echo is a shell builtin

type find

find is /usr/bin/find

type ll

ll is aliased to `ls -alF'

which – displays the path of a command

The which command gives you a file path of a command.

which sort

/usr/bin/sort

whereis – displays path of a command and related documents of the command

The whereis command is similar to the which command but gives you more information.

whereis sort

sort: /usr/bin/sort /usr/share/man/man1/sort.1.gz