Need help, since I am a newbie to scripting .. tia.

I have a file named Rooms.out, which may have the following entries in it. This file gets generated every 30 minutes.
Room1
Room2
...

Depeneding on the entries in Rooms.out, I have to generate another file Exams.out in the following format

Tue Oct 30 04:00:04 Exam is being conducted in Room1
Tue Oct 30 04:30:04 Exam is being conducted in Room2
...

In the next 30 mintes, If Rooms.out has the following entries
Room1
Room3

in the Exams.out file, I have to add a new line for Room3 and delete the line which has Room2.

Thanks.

This page has links in the left-hand margin that describes how to do many common tasks in linux

http://lowfatlinux.com/linux-compare-files-diff.html

Your task seems like searching for and replacing regular expressions, so maybe this one will help:

http://lowfatlinux.com/linux-sed.html

Thanks for the links. It did give me an idea of what I am trying to achieve.
But, I actually need some help scripting itself, meaning, how I put it in a script. If I can get some handhold in starting to write the script that will be great. If this is not the correct forum for that, please redirect me to the appropriate one. Thanks.

Here is a basic introduction to shell scripts in linux:

http://www.freeos.com/guides/lsst/

specifically,

http://www.freeos.com/guides/lsst/ch02sec01.html

also---an excellent book is "Bash Guide for Beginners"----free at http://tldp.org

Easy way to get started:

Practice with individual commands in the terminal.
Then, open an editor and type:
#!/bin/bash
<some command>

Save the file and use chmod to make it executable, then run it using:
./filename

Keep adding commands to the file and you will be building a script.

Where are the timestamps in Exams.out coming from? Can they be re-generated at a later time?

Is the text " Exam is being conducted in " a constant?

How far have you gotten? -- Do you have any sample code for us to critique?

Maybe I'm simplifying this way too much

So rooms.out will contain only the rooms we care about right?

seems to me a simple

for i in `cat rooms.out` ; do echo `date` exam is being conducted in $i ; done > Exams.out

would work. if you want the date formatted do a man date and pick how you want.

I think a script that runs that code put in cron to run every half hour would be the perfect solution. the orginization of cron varies from distro to distro so we'll need to know what distro this is to help you with the cron entry

Not if there is a need to maintain the orig. timestamp for rooms that are in use for more than 1/2 hr. -- as implied by the example in the OP.

To my "Where are the timestamps in Exams.out coming from? Can they be re-generated at a later time?", maybe I should add: "Once determined, must they stay the same?"

ah missed that ready for my next hack job?

for i in `cat rooms.out` ; do echo `date` exam is being conducted in $i ; done >> Exams_tmp.out
for i in `cat rooms.out` ; do grep $1 Exams_tmp.out | head -1 ; done > Exams.out
cp Exams.out Exams_tmp.out

Basic logic just in case you need some explaination...
We are appending the current list onto the Exams_tmp.out file (which would contain whatever was in the last round), then take the first instance we find and stick it in the Exams.out (earliest time stamp), then copy the Exams.out to Exams_tmp.out so we are ready next time the script runs.