man pages

Earlier we used the command ls --help to display the long list of options that ls supports. The more common way to look up how to use a program is to look at its "man page", short for manual.

Try opening the man page for ls

man ls

Notice that instead of dumping all of that information to the screen (STDOUT), we instead end up in something called a "pager". You can move up and down in the man page using the arrow keys. When you want to quit the man page, just hit q.

less

We just used less. When you open a man page, it opens up in less, which is a "pager".

A pager is a program used to view but not edit a text file or text stream. Why use a pager instead of a text editor? Sometimes you don't want to be able to edit a file (changing man pages is a bad idea). It's also much faster when dealing with a very large file. A pager can begin to display the beginning of a file while the rest of it is being loaded in to memory. A text editor has to first load an entire file before it can display any part of it.

We'll look at a few more ways that less can help you in the exercises in the next section. First, let's take a quick pass through the movement commands that less supports.

To do that, we can open up another man page. How about sort?

man sort

vi movement commands

vi or vim is a popular and powerful command line text editor. It's also notoriously difficult for beginners. It's too much to try to learn vi on top of everything else we're going to look at, but we do need to look at a few vi commands.

Why? Because a lot of *nix programs inherited parts of their interface from vi and you'll need to know how to interact with them. less is just one of those programs.

Command	Action
j or Down Arrow	Down
k or Up Arrow	Up
q	Quit
g or <	Go to top
G or >	Go to bottom
/	Search for