Shell Programming and Scripting

Hi,
I am really new in the shell script, but it is really useful for me to learn.
I have one question,
I have a large text document (actually few of them), inside there are lines with information about energies, between 10 to 20 of this lines, varies from one doc to another one, my questions are, using the bash shell
1. how can I selectively choose the last one? (to be printed out in a new doc)
2. How can I selectively choose the one before the last and the one before that one as well?

Thanks for any help

use head and tail commands to get the desired results.

Code:

last line : tail -1 filename.txt
line before the last : tail -2 filename.txt | head -1

You can also use sed to go to any perticular line.

It might be important to note that I am not looking for the last line, I am looking for the last energy which is far away from the last line of the document. Thanks

could you please post your sample data and the output you desire ?

You'll need to post a sample of your file in order for someone to answer your question. Assuming that the energy information spans multiple lines in the file, please post a sample of a complete set of the energy data and a few lines that precedes and follow the data. Without these kinds of examples it is impossible to help.

Here is a file sample, since I do not how to attach a Doc file here (if possible), I am attaching the dropbox link.
---https://dl.dropbox.com/u/63216126/6dialkene.out--
If you grep "E(" you will find a series of energies, the name in between the parenthesis changes from file to file, the number of energies varies from file to file. I need the last energy and the two before that.
Also since I am attaching the file here I would like to ask an extra question. If you grep "input orientation" you will also find a series of XYZ coordinates, how can I find and copy the last one and the two before that, using a bash shell script as well, but separate from the energy script.
Thanks a million for the help.

Moderator's Comments:

edit by bakunin: as new users aren't allowed to post URLs (this changes as you get more posts) i have edited the link in there for you.

Also, and just as important, show us your desired output. If pasted here, enclose with code tags to preserve formatting.

Regards and welcome to the forum,
Alister