In Linux, pipes connect the standard output of one command
to the standard input of another command.
Consider the ls command that was discussed
earlier. There are plenty of options available with
ls, but what if the contents of a directory
scroll by too quickly for you to view them?
View the contents of the /etc directory.
How do you get a closer look at the output before it moves off the
screen?
One way is to pipe the output to a utility called
less. Known as a pager,
less allows you to view information one page (or
screen) at a time.
Use the vertical bar (|) to pipe the commands.
Now we can view the contents of one /etc screen
at a time. To move forward a screen, press [Space]; to move
back a screen, press [b]; to quit, press
[q]. You can use the [left] and
[right] arrow keys to navigate as well.
 | Tip |
|---|
| | To read startup messages more closely, at a shell prompt, type
dmesg | less. You will be able to read the file
one screen at a time. To move forward, press the
[Spacebar]; to quit, press [Q].
|
Pipes can also be used to print only certain lines from a file. Type:
grep coffee sneakers.txt | lpr |
This will print every line in the sneakers.txt file that
mentions the word "coffee" (read more about
grep in the Section called The grep Command).
The main difference between more and
less is that more
only lets you move forward through a file and
less lets you move backward and forward.
List the contents of the /etc directory using
ls and more.
Use the [Spacebar] to move forward through the
pages. Press [q] to exit.
