From the monthly archives: May 2012

A Small Good Habit of Equality Test

By On May 30, 2012 · Leave a Comment

Many programmers make mistakes at times by writing “=” instead of “==” in equality test. A good habit of programming is to write the constant first. For example, if we want to test if the length of a string is equal to 0. Instead of writing

strlen(x) == 0

We can

write 0 == [...]

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Selective Decoding–My Master Thesis Project

By On May 25, 2012 · Leave a Comment

Finally, it’s done!

Work full-time and study part-time can be touch sometimes. But after 2 years of hard working, I’ve made it through.

My thesis is about selective decoding. As the name suggests, decoding video selectively. Zoom interface has been available for photos, web pages and maps, but few players support zoomable video. [...]

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Linux Environment Variables in Bash Scripting

By On May 24, 2012 · Leave a Comment

0. A Stupid Mistake

I wrote shell script from time to time, but never learned it seriously. So I wrote a script contains lines as below,

#!/bin/bash
PATH=”/”
ls -l $PATH

And then I got this error,

./test.sh: line 3: ls: command not found

I struggled a little bit and suddenly realized long time [...]

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A Simple Trick for Grep

By On May 23, 2012 · 1 Comment

grep is a great tool to search strings. I often use grep to check if a specific process is running or not. For example, we want to check if sshd is running, the command would be,

ps -ax |  grep sshd

In my computer, this gives the following output,

755 ?        Ss     0:00 [...]

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How to Set Up SSH Tunnel

By On May 23, 2012 · Leave a Comment

I was setting up a distributed monitoring system recently. At local machine, I has a program named “proga”, trying to access a remote server named “remote” at port 5667. However, the port is blocked by the enterprise firewall.

This is easy to solve by SSH tunneling.

ssh -f roman10@remote -L 5668:remote:5667 –N

This [...]

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Enable Caching on Mobile Devices

By On May 16, 2012 · Leave a Comment

I’ve been working on a project that enables caching on mobile devices. Two different approaches are studied, explored and implemented.

The first approach is to implement a transparent caching system. The caching system will behave like a transparent proxy, and the traffic for user specified apps will be intercepted and examined. If the content [...]

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Turn the Selfishness of Individuals into Good of Public

By On May 15, 2012 · Leave a Comment

This was a ancient Chinese story regarding Zeng guofan (曾国藩). Zeng is a military general and Confucian scholar in Qing Dynasty. He has a large group of counselors working for him. But one thing bothers him is that a lot of people leaves after working for a short period. One day, he asked one of [...]

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How to Deploy Android NDK Library in Separate APK

By On May 1, 2012 · Leave a Comment

There’re times developers want to deploy a NDK library in a separate APK. A typical use case is your library is big and it has different versions for different CPUs/phones. A naive strategy is to put all those libraries in a single huge apk and get lots of user complains. A better approach is [...]

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