Linux Dummies 9th

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Part IV: Junior Administrator Boot Camp
The cat command (and more) is explained in Appendix A.
Note that if you type ls -l > listing again, the data is overwritten,
meaning that the file’s contents are wiped out and replaced with the new
output. You can avoid this situation by using >> as your redirection operator,
which tells bash to add the command’s output to the end of the specified
file. If you type ls -l >> listing in the same directory after making no
changes, the contents of listing are as follows:
rich@testbox:~$ ls -l
total 36
drwxr-xr-x 2 rich rich 4096 2009-05-20 18:56 Desktop
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Documents
drwxr-xr-x 4 rich rich 4096 2009-05-17 17:42 GNUstep
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Music
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Pictures
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Public
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Templates
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Videos
rich@testbox:~$
rich@testbox:~$ ls -l
total 36
drwxr-xr-x 2 rich rich 4096 2009-05-20 18:56 Desktop
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Documents
drwxr-xr-x 4 rich rich 4096 2009-05-17 17:42 GNUstep
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Music
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Pictures
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Public
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Templates
drwxr-xr-x 2 rich rich 4096 2009-05-17 14:09 Videos
rich@testbox:~$
Laying pipes
Another bash shell feature enables you to connect commands so that the
output of one becomes the input for the next one. This feature is referred to
as a pipe. Suppose you want to look over the details of all the files in the /
etc directory in long-listing format. If you type ls -la /etc to do so, a
massive listing appears, and much of the information scrolls right past you.
Although you can back up a bit by pressing Shift+PageUp, you may not be
able to see everything you want to see.
To see all the information, you can do one of two things:
✓ Send the data to a file with redirection by typing something like
ls -l /etc > ~/etclisting — and then review the contents of
~/etclisting with your favorite editor.