Padding zeros in a string

Attention though if your input string has a leading zero!
printf will still do the padding, but also convert your string to hex octal format.

# looks ok
$ echo `printf "%05d" 03`
00003

# but not for numbers over 8
$ echo `printf "%05d" 033`
00027

A solution to this seems to be printing a float instead of decimal.
The trick is omitting the decimal places with .0f.

# works with leading zero
$ echo `printf "%05.0f" 033`
00033

# as well as without
$ echo `printf "%05.0f" 33`
00033

Seems you're assigning the return value of the printf command (which is its exit code), you want to assign the output of printf.

bash-3.2$ n=1
bash-3.2$ n=$(printf %03d $n)
bash-3.2$ echo $n
001

Use backticks to assign the result of the printf command (``):

n=1
wget http://aolradio.podcast.aol.com/sn/SN-`printf %03d $n`.mp3

EDIT: Note that i removed one line which was not really necessary. If you want to assign the output of 'printf %...' to n, you could use

n=`printf %03d $n`

and after that, use the $n variable substitution you used before.

to avoid context switching:

a="123"
b="00000${a}"
c="${b: -5}"