tmux, a Better Terminal Multiplexer than screen

Recently I encountered a program called tmux which claims to be better at "terminal multiplexing" than screen. I did not have any idea about "terminal multiplexing", but I had been using screen for quite a few years now. tmux promises to be better that screen according to the tmux sourceforge page. This got me interested.

I installed tmux, and have been using it since last 2 weeks. My experience has been great except for a minor hiccup between vi and tmux. I thought of writing a small tutorial, but I feel there are better and more detailed ones that I would have the patience to write; not to mention we all "stand on the shoulders of giants". So I am going to point you to the online resources:

• tmux tutorial at hawkhost in two parts, getting started and advanced -- please do not copy-paste from the website as it has some template issues, type the commands instead
• archlinux page for tmux -- a detailed step by step guide containing more information that the hawkhost one
• another step by step guide for getting into tmux discussing advantages over screen and a set of common config parameters

Finally, tmux is quite good and it gives some features not in GNU screen. Unfortunately, tmux is not as popular as screen, so you should be able to use both. Here is my contribution to the community, a cheat sheet with popular commands for both tmux and screen together. Please note that I use Ctrl+a as my tmux hotkey rather than the default Ctrl+b. Here is the thing you have to add to your ~/.tmux.conf to achieve this:

unbind C-b
set-option -g prefix C-a

Copy-pasting in tmux is also quite easy. You can copy from any part of the command window. Go to the copy mode by Ctrl+a PageUp. Move around the terminal using arrow keys. Ctrl+Space to start marking the text from where you want to copy. Use arrow key to select text. Alt+w to copy the text. Paste text using Ctrl+a ].

Thanks for reading.

Reload .inputrc at runtime

If you have been playing around with bash for some time you must have changed the file .inputrc sometime. I have changed it several times mostly for Del key and auto-completion trick. However every time I change it I have to logout of bash for it to take effect. Here are two different ways to do the same without logging out of the shell.

1. Keyboard shortcut : Ctrl+x followed by Ctrl+r
2. Script : bind -f ~/.inputrc

Here is an excerpt from my .inputrc which many others might find useful:

"\e[1~": beginning-of-line          # home
"\e[3~": delete-char                # delete
"\e[4~": end-of-line                # end
"\e[5~": history-search-backward    # page-up
"\e[6~": history-search-forward     # page-down

Hope this helped you.

Brilliant 8-phase multi-quine in ruby

Wikipedia defines quine as:

A quine is a computer program which takes no input and produces a copy of its own source code as its only output.

In layman terms, it is a program that when executed outputs itself. Like a C program outputting its own source code. Kleene's Recursion Theorem proves the existence of quines in any Turing Complete Language. Its a good exercise to write one in your favorite language. Its fascinating to see quines.

Today morning my friend Umesh showed me this brilliant piece of ruby code that behaves as a Multi-quine. Link to original post by its author. Here's a listing of the same:



Save it as "test.rb" and run the following shell script:

while true;
do
    clear
    ruby test.rb | tee test2.rb
    mv test2.rb test.rb
    sleep 1
done

You will be able to see the picture changing after every 1 second and returning back to the original after 8 seconds. Note that when you run test.rb, it produces the output which is used for the next iteration. The shell script code lines 4 and 5 runs the code and uses the output of the code to replace the original code.

After being amazed by the beauty of this piece of code, I am not trying to figure out how exactly does it achieve this result. Someday I will post the same code with indentations and explanations in this blog.

Make Your Own Command-line Calculator with bc

I do not know about you, but I am bothered by the lack of a proper command line calculator for doing small single line calculations in Linux (or any other UNIX or Mac system). Sure bc is there but it does not support floating point by default, so one ends up writing things like:

echo "scale=3; 22/7" | bc

which is quite cumbersome for day to day work.

To subvert this trouble, I wrote the following two-liner and saved it as "calc" in a directory in PATH:

#! /bin/bash
echo "scale=3; $1" | bc; exit

Then do a "chmod +x" on the file to give it execute permission. This does the same thing as the above script, but is way simpler to use:

calc 22/7

The command "scale=3" was to instruct bc to print upto 3 decimal digits. You can change it as per your requirements.

The bc utility can do way more than this simple calculations. For example it can handle different bases and load functions from files. To know more about its capabilities try the good old "man bc" in terminal or read an online reference like this one on about.com.  You can read more about its advanced capabilities from an old but quite relevant article in LinuxJournal "bc: a handy utility".

Disclaimer : Although the script was by me, the idea is not new. In fact a lot of my colleagues use similar scripts for their own daily work.

Do-while loop in Ruby

As you know, I'm trying out Ruby. While solving one of the exercise problems I felt the need for a do-while loop. Unfortunately ruby has no documented do-while loop. Thankfully, somebody has already asked this same question in stackoverflow : Is there a do-while loop in ruby?

Here is a demonstration of a do-while code in ruby:


Remember that using undocumented features is always ill-advised !!