View source for Shell

A shell is both a command language and a programming language ([[interpreter|interpreted]]) that provides an interface to any UNIX based operating system [[UBO]]. 

The most popular shell by far is [http://www.gnu.org/software/bash/ bash] which is provided by the GNU team. There are several other popular shells, depending on your requirements and skillset:

* csh
* tcsh
* sh
* ash
* zsh

to see what shell you are using:

 $ echo $SHELL

which is one of the [[variables]] that can be found in your ''env''ironment. You can get a list of all of your environment variables:

 $ env

as you can see, there is where you will change items such as your [[PATH]]


== Scripting ==

If you want to learn shell scripting, we recommend you start with [[sed]], [[awk]] and [[grep]]. All three are very powerful and each will take years to master. An example of each:

This will substitute any line with the word root in it in /etc/passwd with an empty space in place of "root":
 $ [[sed]] s/root//g /etc/passwd

This will show you the fifth field in /etc/passwd if you seperate each field with a colon:

 $ [[awk]] -F: '{print $5}' /etc/passwd

Finally, this will show you every line in /etc/passwd with the word "root" in it
 $ [[grep]] root /etc/passwd