Batch Mp3 Converter Shell Script

Hi,

Use the lame encoder.  The command you need is:
lame --mp3input -b 256 <file_in.mp3> <file_out.mp3>
So from the command line you would cd to the directory where the files are and type:
for FILE in *
do
   lame --mp3input -b 256 "$FILE" <path_to_output_directory>/"$FILE"
done
What this means is for every file located in this directory, pass the file-name to lame, using the variable FILE.  We place the variable in quotes to "escape" the spaces, so that the shell does not recognize the spaces in the file-names as additional parameters.

So now to place this in a shell script, create a file with the following:
#!/bin/bash

INPUT_DIRECTORY=$1
OUTPUT_DIRECTORY=$2

for FILE in $INPUT_DIRECTORY/*
do
  lame --mp3input -b 256 "$FILE" OUTPUT_DIRECTORY/"$FILE"
done

This file is a shell script that starts off identifying the shell it'll use (#!/bin/bash) - this is mandatory for shell scripts and Linux supports many, many different shells.
Next, we take the parameters passed to the shell script, the first one ($1) being the source directory that you user has provided on the command line and assign it to the local variable INPUT_DIRECTORY (I do this for clarity).  We then do the same for loop as we did before on the command line.  There's a lot of things I've left out, such as checking that the user did provide arguments and that they are legal arguments (i.e.: real directories) and that they are readable and/or writable, or if the user swaps the location of the read and write positional arguments.  Another thing to note is that if the user provides an argument such as /home/me/srcmp3/ (note the tail ending /) that would expand in the shell to for FILE in /home/me/srcmp3//* which is probably a bad idea.  Another problem could be where there is a space in the directory name(s), we could just place a quote around that, but the user could pass the arguments escaping the space already and the shell would interpret as a literal (with the escaping loosing it's special meaning).  Like I said, I've kept this *very* simple.

Anyway, once you've created the file, you need to make it executable, which you can do by typing chmod u+x <name_of_file>.  So say we created our file as convMp3.sh we would type
chmod u+x convMp3.sh

To execute the file we would call the file (by the full path - there are other ways of doing it but I am trying to keep it simple) and pass the arguments as required, such as:
/home/me/convMp3.sh /home/me/srcmp3 /home/me/dstnmp3
This would call the script convMp3.sh located in /home/me/ with the arguments input directory: /home/me/srcmp3 and output directory: /home/me/dstnmp3

The best place (in my opinion) is to start at the bash how to, which can be accessed here: http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html

Hope this helps