Category Archives: Unix

Easy Way to Create Colorful Bash Prompt

The Problem

I often want to fiddle with the bash prompt, but don’t want to deal with bash prompt escape sequences. I wish for a utility which simplify setting a bash prompt. I finally wrote that utility myself: mkprompt


Copy mkprompt to a directory in the path.

Using mkprompt

The best way to show mkprompt usage is via a couple of examples.

PS1=$(mkprompt "red workdir" space dollar)  
PS1=$(mkprompt "cyan Workdir" space "green dollar")  
mkprompt # display help

For more information, see my shell_tools page.

What’s Next?

The following are improvements which I plan for mkprompt, depends on my free time:

  • Implement the rest of the prompt escape sequences
  • Improve the help output
  • Implement installation script

The Script

I current host my script as part of my shell_tools collection on GitHub.


New Life for Old Laptop

In this article, I am going to discuss ways I gave my five-year-old laptop a new life.

In 2007, I purchased a used laptop to learn .NET programming. Since it was an old laptop, the machine barely had enough horse power to run Windows Vista. Soon, my job no longer require .NET programming, I promptly wiped the hard drive and installed Ubuntu Linux on it. What a difference does that make! My laptop started much faster, ran applications quicker and I did not have to worry about malware, trojan, or virus. Life was good.

Fast forward to last year, after several updates, my laptop was running a current version of Linux Mint, but it seems not fast enough. At that time, I had two choices: upgrade my memory from 2GB to 4GB, or upgrade the hard drive to SSD. After a little research, I decided on the later. I ordered a 40GB SSD drive for about $100. Again, the new drive blew me away: I was able to boot up my system in about 37 seconds (including the time to type the password). Applications now start much more quickly than before. I even compare my laptop with those of my brothers and it blew the newer laptops away. Yes, I know I am comparing apple with orange (Linux vs. Windows, SSD vs. hard drives). My laptop now makes an excellent machine for daily use: Facebook, email, web, watching videos, and development (scripting, C, C++).

In summary, if you have an old laptop, don’t hesitate upgrade it to SSD and install Linux on it (I recommend Linux Mint for ease of use). You won’t be disappointed. Not only your machine will run much faster than before, you get peace of mind knowing that your machine is realatively safe from malware and the like (relatively because there is no such thing as absolutely safe operating system).

My Brief BSD Adventure

I was bored. My old laptop has been running Linux Mint for a while and now I want something different so I checked out BSD, PC-BSD to be more specific.

In the past, I have been flirting with BSD several times, and ended up abandon BSD for Linux. This time is no exception. Before going into the bad parts (at least for me), I would like to state that PC-BSD 8.2 is an excellent OS. The installation is smooth and trouble-free, unlike my previous encounters. The default KDE window dressing are attractive and clean looking. Overall, applications are fast.

There are a few things that I subjectively found not up to my taste; again, the keyword here is subjectively. The default shell for PC-BSD is csh, but my choice is bash, so I changed it at installation time. PC-BSD uses KDE as its primary window manager; personally, I like gnome better. The default installation includes Tcl 8.5, but it is called tclsh8.5, without any softlink to tclsh at all. I had to create that soft link myself. On most Linux systems and on the Mac, the shell is called tclsh, simply enough.

Now, comes the things that drove me nut for the two days I ran PC-BSD. First off, after installation, I ran software update. After reboot, I logged into KDE and found a screen with just a wall paper, nothing else. I tried alt-tab and saw a bunch of applications in the task list, but none of them is visible. I tried to fix it for two hours and finally gave up and ended up re-installing the OS from scratch.

I then left my laptop unplugged and went to sleep as it was late. The next day, I turned on my laptop and found that the battery was drained, so I plugged the power cord in and turned on the laptop. I thought the laptop was in hibernation; but it booted up as if it was turned off. That means I lost my works from the previous night (a couple of C++ files). I thought PC-BSD should have hibernate the system when battery went down. Furthermore, the power saving should have sleep, then hibernate the system, in order to save battery in the first place.

Worse yet, once booted up, I could no longer connected to my WIFI access point. Fast forward until the afternoon, I gave up my hope and gave up on BSD one more time. I was going to try Fedora 15 next.

Besides these annoyances, there are a few things about PC-BSD that I don’t like. On my 1.66GHz core duo laptop with a 40GB SSD, my Linux Mint 11.04 boots up in about 38 seconds. Fedora 15 does it for about 48 seconds. However PC-BSD took its sweet time to about 2 minutes and 37 seconds.

The default Linux Mint installation allows to use the right- and bottom edge of the trackpad to scroll. Fedora 15 allows to choose between using the edge or two fingers. However, PC-BSD does not allow to scroll using the trackpad. I am sure, eventually I will find out, but I wish they offer scrolling in the default installation.

These are a few things that prevent PC-BSD from becoming my primary OS. I hope that PC-BSD 9 will be much better. When it comes out, I will give it another try.

Better Font and Color for tkcon in Linux Mint 11

The Problem

In Linux Mint, the default font and background color for tkcon is terrible. I want to change that to something easier to read.

The Solution

Here is my ~/.tkconrc, which fixes it by choosing a better font and background color:

set ::tkcon::COLOR(bg) ivory
set ::tkcon::OPT(font) "{Liberation Mono} 10"


The default font in Linux Mint is terrible: it is hard to read and pixelated. I found the Liberation Mono font works best for me; your mileage may vary. Also, the default background of gray is somewhat dark and drepressing, therefore I changed it to ivory, which is an off-white color (at least on my old laptop).

Automatically List a Directory’s Contents After Changing Dir

The Problem

After the cd command, the next command is almost always ls so we want to combine the two to automatically issuing the ls command right after the cd command.

The Solution

In bash, add the following line in either ~/.bash_profile or ~/.bashrc:

function cd() { builtin cd "${@:-$HOME}" && ls -l; }

If you are using csh or tcsh, add the following line to .cshrc:

alias cd 'cd \!*; ls -l'

Now, whenever we type a cd command, not only we are changing the work directory, but also list the files at the new location. I would like to thank Matt Jenkins for helping me out with the csh part.

Squeeze Multiple Blank Lines within vim

The Problem

I want to squeeze multiple blank lines into just one while editing in vim. I often receive source code which the author used multiple blank lines to separate functions. I don’t mind if functions or code block are one or two lines apart, but I have seen sources where functions are four or more blank lines from each other. This is annoying and I want to squeeze many of them into one.

The Solutions

The obvious solution is to use vim’s search-and-replace feature, as discussed in this post. However, my regular expression skill is very basic and I tend to forget the syntax when I need it. Hence, I devised my own solution, one which I have better luck memorizing.

My solution involes the cat command:

:%!cat -s

This short little command applies ‘cat -s’ on my entire file contents, which squeezes multiple blank lines down to one. Note that this solution will only work on Unix-like systems such as BSD, Linux, and Mac OS X. It does not work on Windows. This is one of the shortcoming of this method compare to the previous one.

How to Configure WGet to Work with Proxy Server

The Problem

I want to configure WGet to go through a proxy server without having to specify that on the command line

The Solutions

The first solution is easy: I can set a shell variable called http_proxy. Here is an example in bash:

$ http_proxy=http://proxy-server:8080
$ export http_proxy

Another solution is to place this information in a configuration file called ~/.wgetrc. Here is a sample:


If you have administrative rights and want to configure the system-wide behavior, then place the above line into the file /etc/wgetrc.


This is a very simple configuration problem, but it took me a while to figure out because I assumed that my system came with proxy pre-configured, but it was not. If you use wget on your system and it took a long time to get some trivia file (for example and you are sure that your internet connection is working fine, then you might have a proxy problem. Normally, you only encounter proxy servers at work, school, or other organization, but not at home.