Writing binary files with bash

Hello,
I'm trying to see if I'm able to write some binary file using bash. So, when writing a binary file you often want to write a number into binary format. I ended up with this simple function for writing numbers in little endian:

function num2bin() {
   printf $(printf %.$(($2*2))x\\n $1|
        sed 's/\([0-9a-f][0-9a-f]\)/\\x\1/g')|
        awk -F '' '{ printf $4$3$2$1 }'
}

The first parameter is the number to write, the second is the number of bytes (up to 4). For example "num2bin 40 4" will output a 4-byte long string containing the number 40 in little endian.

How do we use it? I wrote an example script for creating a wav file with noise (according to wav specifications) that you can read here.

Let me know if you have a simpler version of the num2bin function.

Complete variables with cd command in bash

Hello,
lately I've been searching for a way to complete variables containing directories with the "cd" command in bash. This is very helpful if you have something like "cd $mydir/". This is not actually working in debian bash-completion.
Then I've realized that other commands such as "ls" actually expand variables. I looked for some "complete" combo used for "ls" but not for "cd" in /etc/bash_completion and I came out with the following:

complete -F _longopt -o default cd

Luckily, this is exactly the command needed to enable variable expansion with the "cd" command. Put that in your .bashrc after loading bash_completion and you're done.