The Chrisonomist

Timeline

2009

2008

Interests

Philosophy

This section contains a couple of my philosophical writings.

Projects

This section contains a presentation of several of my more interesting and better implemented projects.

Hacks

Presented in this section are smaller hacks that are not large enough to be considered projects. Most of these hacks are pieces of code that I quickly conjured in several hours to automate a tedious task.

These unrefined works are made available in hopes that you will find them useful. Please let me know of any bugs that you find or any suggestions that you think would improve the code.

SIP telephone ringer

Small program that sends a SIP invite packet to a specified telephone, ringing it. Useful as a wake-up dialer when combined with a cron daemon.

Download

Hard disk backup over several smaller files

Using the UNIX dd tool, a hard disk drive can be copied to a file and later restored back to the disk. However, the file that is being used to store the hard disk image may have limitations. For example, it may reside on a FAT32 filesystem, in which case it has a maximum size limitation of 2GB, or it may reside on a CD-ROM. I wrote two shell scripts that split the hard disk image over several files.

The scripts are designed to be run on a UNIX system, using Slax for instance. Note that host operating system on the hard drive to be imaged is irrelevant -- the scripts merely need to be run under UNIX.

For the gzip compression to be useful, the unused portions of the hard drive must have low entropy. One way to achieve this is to write large homogeneous files to the file system, for instance a 2GB file consisting of all zeros. The compression is good --- a 20GB disk with a single Windows XP partition, 2GB full, fit into a 1.2GB image.

ReiserFS filesystem recovery on a disk with bad blocks

In an act of stupidity, I performed an rm -rf * on my home directory, by accident. I immediately attempted to perform a file recovery by unmounting my reiser file system /home partition and attempting a reiserfsck --rebuild-tree -S /dev/hda3. This process turned into quite an ordeal.

My partition had quite a few bad blocks that the file system didn't know about. reiserfsck terminated upon reaching the bad blocks. Next, I attempted to run badblocks -b 4096 -o hda3.bb -s /dev/hda3 to generate a list of badblocks to pass to reiserfsck. After many hours, I had a list of bad blocks; however, upon being passed this list, reiserfsck determined that several of the blocks were journal superblocks, and again terminated.

At this point I wrote the code that fixed my problems and allowed me to recover most of my files. There are essentially two #define options, NOSUPERDIE and NODIE. If NOSUPERDIE is 1, then upon encountering a bad block, reiserfsck does not terminate, but rather performs a destructive write to the bad block. Modern hard drives remap the block to a working block upon a destructive write. This is useful for remapping bad journal superblocks. The second option NODIE, causes the bread function to dynamically avoid badblocks, as if the blocks had been passed via the -B option. This significantly decreases the time necessary to perform bad block checks.

Batch renaming of files

Different people have different ways of naming files. Some people use spaces, capitalization, and other punctuation in filenames. Downloading files from various sources creates a quagmire of filenames. This loss of clean standardization is frustrating. More importantly, spaces often act as argument delimiters and punctuation often has special mean in scripting languages.

I wrote a small bash script called rmspace to remedy this problem. This script takes multiple files, for example via rmspace *, and removes capitalization and punctuation. Additionally, spaces are replaced with underscores.

Puzzles

Below is a collection of a variety of mind puzzles that I have come across. Unless otherwise noted, I am not the original author of each puzzle, and each puzzle has a legitimate answer. In other words, the solutions are not clever circumventions of the stated conditions. Have fun!

• Find the next number in the pattern: 1, 11, 21, 1211, 111221.
• Using the numbers 1, 3, 4, and 6 exactly once, find an expression equal to the number 24. The expressions may only use the basic arithmetic operators, namely addition, subtraction, multiplication, division, and parenthesis for changing the default priorities of the operators.
• Four people need to cross a bridge in 17 minutes in the dark. Up to two may be on the bridge at a time and they must cross carrying a flashlight to see treacherous obstacles on the bridge. The times that it takes for each person to cross the bridge are 1, 2, 5, and 10 minutes. What sequence should they cross in to make it in the alloted time?
• There are two ropes that each burn completely in exactly one hour, though each burns at a different, unknown, non-uniform rate. Using a lighter and the two ropes, devise a method to time a 45 minute interval.
• There are nine balls, one of which is heavier than the others. Using a balance beam, devise a weighing process to find the heavy ball in only two weighings.
• A traveler arrives at a divergence in the road, one path leading to the town of Alpha, the other leading to the town of Beta, but he doesn't know which one leads to which town. Fortunately, a citizen from one of the two towns is working on a problem set at the divergence. However, citizens from Alpha always tell the truth while citizens from Beta always lie. What one question can the traveler ask the citizen to determine which road leads where?

More good monthly puzzles can be found at IBM Research Watson.

Quotations

• "To pour forth for the common good is divine." - Benjamin Franklin
• "Variety is the spice of life." - Axel Scherer, professor of electrical engineering, Caltech.
• "To every man is given the key to the gates of heaven. The same key opens the gates of hell." - Richard Feynman, quoting man from Hawaii, in reference to nuclear power.
• "Capitalism is communistic." - Ed McCaffery, professor of law, Caltech
• "Get busy living, or get busy dying." - Morgan Freeman, The Shawshank Redemption
• "I have to remind myself that some birds are not meant to be caged, their feathers are just too bright. And when they fly away, the part of you that knows it was a sin to lock them up does rejoice, but still the place you live in is that much more drab and empty when they're gone. I guess I just miss my friend." - Morgan Freeman, The Shawshank Redemption
• "Monarchy is a family business." - John Brewer, professor of history, Caltech
• "I'm all for experimentation, as long as I'm not the lab rat." - Me
• "You can spend all your time getting gear... but in the end you just don't feel happy." - My room mate John while he was off playing Halo
• "Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." - Brian Kernighan, heard via Glen George

Contact

E-mail: chiszp[at host]alumni.caltech.edu

Telephone (SIP): sip:17470450318@sipphone.com
Telephone (PSTN): (202) 470-3814