In UNIX you can direct the output of a command to either a file, or another command.  Huh?  That's right. 

So, lets start with some data we can play with:

 mkdir -p ~/LL/lesson2    <- the "~" is the same as "/home/<username>"

 cd ~/LL/lesson2

 cd lesson2

 wget http://biff.freeshell.org/learnlinux/examples/lesson2.txt  <- downloads lesson2.txt to the current working directory

so, some basics:

1- cat lesson2.txt

reads lesson2.txt and prints each line to the screen

2- cat lesson2.txt > outfile

Reads each line of lesson2.txt and writes it into the file output instead of to the screen

2- echo "this is a test" >> output 

The ">>" operator means append.  If you look at the bottom of the file output, you'll now see "this is a test"

3- echo "this is another test" > output

You'll notice that you've replaced the contents of the output file with just "this is another test".  The ">" operator deletes the file if one exists, and simply creates a new file.

So, lets learn the sort command:

cd ~/LL/lesson2

wget http://biff.freeshell.org/learnlinux/examples/list.txt

cat list.txt   

Let me give you a few examples:

1- sort list.txt

   puts list.txt order

2- sort < list.txt

redirects the input of list.txt to the sort command (it looks the same as the above command)

3- sort <list.txt > outlist.txt

this directs the input of list.txt to the sort command, and then directs the output to the outlist.txt file

4- sort < /etc/passwd

   puts the /etc/passwd file in order

read: http://www.ee.surrey.ac.uk/Teaching/Unix/unix3.html

and

http://www.ee.surrey.ac.uk/Teaching/Unix/unix4.html

ASSINGMENT:

1- the last command shows you who has been logged into the system, sort in order the users that have logged in.

2- tell me how to ignore case for the sort command

3- tell me how to reverse the output of the sort command

4- show me how you would list the files of the /etc/ directory in alphabetical order

5- show me how you would list the files of the /etc/ directory in reverse alphabetical order