It depends on what you are trying to do.
Shell scripting is quite limited in what it can do when compared to a more general purpose scripting language such as Perl or Python. Nothing wrong with that and I have used shell scripts a lot when I was a Unix admin but for networking most of what I have seen in terms of script languages has been TCL, Perl and Python.
You can use scripts to automate logging on to devices and executing commands, basically the script does what you would type in. To do this you can use Expect and Perl, Python and TCL all have Expect functionality (Expect was originally an extension to TCL).
But you are still just basically automating what you yourself would type and you would run these scripts from a server, PC etc although if you have a lot of devices you need to update with the same details it can save a considerable amount of time and just as importantly if the script works it removes the human error element of configuring multiple devices and perhaps getting a few wrong.
The next step is EEM where the device has an inbuilt TCL interpreter which means you can write applets or scripts that are stored on the device and can respond to specific things happening eg. if an interface goes up or down or the routing table is changed you can execute a set of commands.
There is an EEM forum on here.
I believe also that Nexus switches have an inbuilt Python interpreter which allows pretty much the same thing.
The advantages of the interpreter being on the device is that it saves a lot of extra coding and you can get more information because Cisco have added libraries to those interpreters which are specific to the device and which provide you with a standard set of APIs which your script can use.
As I said scripting can save a lot of time and there is an argument that all network engineers should at least now some scripting and this has become more of a hot topic with the promise of what SDN can achieve in the future although it has to be said there are already configuration management tools out there which make use of the above languages.
It really depends on what you are trying to do and how much you want to automate things.
In terms of tutorials etc. for all the major scripting languages there are a lot of online tutorials and books you can use.
In addition there are sites where you can run your scripts online but to be honest it is easier to simply download the interpreter to your PC, laptop etc. and you should be able to find a compiled version of the interpreter for whatever OS you are running.
Jon
