January COSI Reports

January 26

Over the course of the past week, I improved update and production scripts for the lab build. Along with regular code clean-ups and documentation, I made the scripts use lock files. It is done by creating a lock file in /var/lock directory when the program starts. The lock file is then removed in one of the following cases:

At the end of the script, naturally
When an error is occurred and the script is aborted, e.g., when AFS service fails to stop
When the script is interrupted from command line, e.g., using Ctrl-C

In the first two cases, removing is done simply with
rm -f $LOCKFILE
In the last case, I had to look up some information on trapping signals in bash scripts. Intuitively enough, trapping is done using command 'trap'. The syntax is

   
trap "command-to-be-executed" SIGNAL_TO_BE_CAUGHT

There are many interrupting signals that can be sent to a running program. The collective name for all of them is 'EXIT'. Therefore, the line I used in the scripts is
trap "rm -f $LOCKFILE" EXIT

Aside: I learned that in order to make sed show the values of shell variables in its search-and-replace syntax, one needs to put double quotes around the query-replacement expression. I.e.,
sed 's/$query/$replacement/' file.txt
will see $ signs as simple characters in query-replacement. On the other hand,
sed "s/$query/$replacement/" file.txt
will substitute the values of $query and $replacement in their respective places before processing the statement.

Mike and I planned ahead for COSI, and came up with some seemingly good ideas.
There is an idea to perform a COSI networking workshop with former COSI members as guest speakers. So far, Eli Dow and Brian Clark have agreed to talk about the ways experience at COSI helped them to utilize their potential to the fullest.
There is also an idea to have teach-your-friends workshops. The scenario would include a group or a single person learning about a particular (hopefully intriguing) subject related to Open Source and then present it to his peers. It would be great if either Mike or Kyle talked about programming in Java. I would really like to learn about it without having to take the course :) I am interested in learning to hack Linux kernel. In particular, I would like to give a workshop on Linux kernel signals.

Rouslan Solomakhin