Recursively rename files in windows

My friend Prasanna B P asked me to solve a bunch of problems that he was facing with his computer. One of them was fairly common and there was a very easy and straight forward brute force solution. But coming up with a "smart" was really interesting.

Essentially some malware had renamed all the movie files that he had to carry a .jpg extension. His initial solution was to associate those jpg files with a movie player like Mplayer123 or VLC and the file would be invariably played without any regard to the extension. But this made the genuined jpg pictures to be opened with the player.

The obvious solution was to rename all the files and change the extension. Manually doing it from the GUI is the brute force idea that I earlier mentioned. And it is a totally crappy one. Next I can rename all files in a directory from the command line. But here the movie files were in directories of their own and hence I would have to move to each directory manually and run the rename command. This makes it as good as the GUI approach. In fact the extra effort of typing the commands might make it worse.

The I searched the internet a little and got to know that the windows command shell supports a "FOR" statement which can be used to recursively traverse directories, amongst many other things it provides. Using that I found this command:

FOR /R %x IN (*.jpg) DO ren "%x" *.avi

from this website : http://stackoverflow.com/questions/210413/command-line-recursive-renamemove-in-windows

People used to Linux Shell scripting might think of this as a wierd syntax, but yeah thats the windows choice.

It was good to do some Windows Shell scripting too. :-)

Profiling (timing) the firefox build process

Its been nearly 2 years since I am building Mozilla Firefox myself on my machines - various machines of varying capacity.

Initially it was a desktop having Intel Pentium 4, Single Core (obviously), 2.6Ghz, 256MB RAM, running Slackware 11. It probably used to take about 1.5 to 2 hours (I do not remember it now). I never profiled that at that time. Getting a mozilla build itself was a big achievement for me.

After that it was another desktop having Intel Core 2 Duo, Dual Core (obviously, again), 2.4 GHz, 2GB RAM, running Windows XP. This generally took about 45 minutes. AFAI Remember, I had several other programs running when firefox was building.

And this discussion of amount of time taken to build firefox came up a few times in IRC and I myself had this wish to time the build process. Off late, that is from about last week this wish became very strong and today finally I did time it, that too on two machines, my laptop and my desktop. This blog post is the result of the these two profiling tasks. Here are the results.

Note: By profiling I did not do any complicated or intricate. I just used the "time" utility which tells how much time the command takes.

1) On my laptop. --- Build was the only application running apart from the services.
Specs:
IBM Thinkpad T60p. (The one which heats up a lot)
Intel Centrino Duo, T2600 @ 2.16GHz, (Dual Core)
2GB RAM
Windows XP Pro SP2.

The results shown by the "time" utility are:

real 36m33.476s
user 4m17.776s
sys 4m36.271s

The build was done in the MingW shell that the mozilla build system provides. I am not sure to what extent these are reliable, but the real time is pretty much acceptable.

Edit:

Today I ran the build command from the history and hence the 'time" prefix got in automatically and the build was timed again. Surprisingly today's times are way away from the last one. Here are the times:

real 74m26.484s
user 9m53.015s
sys 8m18.365s

Well this time a lot of other apps were running. Firefox (2 instances), Chatzilla, Outlook, Several command windows, Komodo Edit (which again is like another firefox), notepad and a couple of explorer windows. So the time being doubled is not a surprise. Guess this just gives a perspective. :)

2) On my desktop --- Apart from the build process, FF with Chatzilla was running and several instances of bash (Terminals) were running.
Specs:
DELL Optiplex 755 (Sleak, powerful, sometimes fragile)
Intel Core 2 Quad, Q6600 @ 2.4Ghz
4GB RAM
Ubuntu, Gutsy Gibbon

And the results are:

real 20m40.497s
user 19m4.320s
sys 1m17.885s


The two sets of times are a little confusing. But real is all that matters as that is how long I have to wait for the build to be ready.

If you are planning a build then this info might help you plan things accordingly.

Happy building.

Camouflage in full action -- Totally mind boggling

Even the makers of the bond movies did not think of anything as crazy as this. This was a real stunner for me.

Making firefox use a little lesser memory

A lot people tell me that firefox uses a lot of memory and it grows like anything when used for a long duration. From the discussions developers and some blog posts/forums it appears the prior to FF3 it was memory leaks which formed a major part of this. Apart from that one of the important features "bfcache - Back/Forward Cache" which, arguably, makes back and forward navigation very fast, uses a lot of memory. In on the pages I read apparently it can be up to 4MB per page. This cache essentially keeps the parsed HTML of the mark-up in the memory along with the Javascript state. Sometimes, or more like most of the times, this can very taxing. You might be the kind of person who does not really uses the Back-Forward navigation and in case you do it you are OK with a slight delay (which may not percievable with a good conenction). If indeed you are that kind then disabling this "bfcache" will probably make your firefox eat lesser memory.

The setting/preference that controls this behavior is : browser.sessionhistory.max_total_viewers

By default it is -1, which is no limit. Setting this to 0 (zero) will disable this cache completely. Essentially you are telling Firefox to not to store the state of any document in the memory. If you want to have this feature with a saner limit you can set it to an integer representing the number of pages you want to be saved in memory.

Like any other pref not exposed through the Options dialog this has to be edited by visiting the page about:config. Open this in a tab and key in (or copy and paste) the preference string. Double click it to edit.

May be you can now lose lesser hair as your other applications will run smoothly. :P

Hari Om.

April 2009 - Appraisal

This was making rounds as email forward. Just could not laughing for a loooooong time..

You and Your BOSS