Getting Help in the Shell

The commands you can type in the shell are almost always the names of executable programs elsewhere in the system. Some shell commands are internal and specific to each particular shell (such as alias), but most commands must correspond to some installed program. The trick in using the shell efficiently is knowing which of these programs does what. That’s where the built-in “manual” comes in. The manual is invoked using the man command, and you can find information on any known command or program like so:

# man ls