sed is great for pattern matching or retrieving lines

Here is a cool example

Say you type df:

The output would be something like:

[quote:3bb8d51437]Filesystem 1k-blocks Used Available Use% Mounted on
/dev/hda2 1712432 1206664 418780 75% /
/dev/hda1 31201 10505 19085 36% /boot
none 30932 0 30932 0% /dev/shm
[/quote:3bb8d51437]

Say you want the second line only you could pipe the output of df to sed
(replace the 2 in '2p' to retrieve a different line)

[code:1:3bb8d51437] df | sed -n '2p'[/code:1:3bb8d51437]

This will return only the second line:

[quote:3bb8d51437]/dev/hda2 1712432 1206664 418780 75% /[/quote:3bb8d51437]


As you can see sed can be very powerful and this is just the beginning of what it can do