Memoization

Memoization is a way to make code run faster by saving
previously computed results. Instead of needing to recompute the value of an
expression, a memoized computation first looks for the value in a cache of pre-
computed values. (caching)

Mathematics for Computer Science

I recommend free online reference:
Mathematics for Computer Science

Bandwith Meter

Here is link for CNET bandwith meter Bandwidth Meter Online Speed Test

restart Drush cron

DELETE FROM variable WHERE name="cron_semaphore";
DELETE FROM variable WHERE name = "cron_last"
drush cc all

Screenlap - share screen instantly

Easy way to share screen. Excellent web application.
Screenlap

od (dumps a file in different numerous system )

od - command dumps a file in octal, decimal, and other formats.

Useful Links:
http://linux.101hacks.com/unix/od-command-examples/
http://www.linuxjournal.com/article/1326?page=0,0

pushd and popd

pushd saves the current working directory in memory.
popd returns to the path at the top of the directory stack.

Example
[sputnik@localhost html]$ pushd . # push current directory to memory
/var/www/html /var/www/html

[sputnik@localhost etc]$ cd /var/games/ # change directory

[mshnaydman@localhost games]$ popd # returns from directory
/var/www/html
[sputnik@imagick-test html]$

For more information, read the Wiki Page

Resize & write data into image

I had task to resize image and add unique identifier. See below handful utilities.

- Exiv2 (manage image metadata. Supports IPTC, Efix, XMP and others formats)
Example: Add the field to IPTC
[sputnik@test_hires] iptc -M"add Iptc.Application2.SpecialInstructions blah blah" myfile.jpg

- Imagemagick (resize, edit, view images or more)
Example: Resize image to 200x200 pixels
[sputnik@test_hires] convert -resize 200x200 myfile_input.jpg myfile_output.jpg

- Identify (image characteristics. is a member of the ImageMagick suite of tools)
Example: Get image size
[sputnik@test_hires] identify -format '%w:%h' $source

- File (determine file type)
Example: Get Filename information. For more 'man file'
file -i $filename | cut -d':' -f 2

Astronomy Lectures

I start getting into Astronomy for last few weeks and find the subject very interested.
Here are 3 lectures by professor David Helfand that I find interesting:

Astronomy Lecture 1: What Is a Star?
Astronomy Lecture 2: Lives of the Stars
Astronomy Lecture 3: Planets Everywhere


There lectures still available in Google Videos.

cd command

Few most useful b commands
cd - # move back to the previous directory
cd ~ # move into your home directory
cd .. # move up one directory