basic sed regex backreferencing q

[diamondracer]

Was wondering if anyone could point me in the right direction here..I have a script that is supposed to append a batch number on the end of a file (before the extension), but I don't think I have the syntax right. For example, if I have a file called:
FILE_Z66_ALPHA.txt
I want the script to change it to the following:
FILE_Z66_ALPHA_BATCH_1.txt

I'm trying to use sed with backreferencing but I don't think my syntax is correct ... does anyone have any suggestions?

#!/bin/bash

for filename in `ls *.txt`
do
new_filename=`echo $filename | sed -r s/\([\S]*\).txt/\1_BATCH_1.txt/`
echo $new_filename
mv $filename $new_filename

done

Thanks !

[ProgramIt]

not sure if this will help much but depending on your file names. if you can guarantee there will only be one '.' in the filename and there are no spaces, you could use this regular expresion

new_filename=`echo $filename | sed 's/\./_BATCH_1\./'`

- John

[ghostdog74]

# a=FILE_Z66_ALPHA.txt
# IFS="."
# set -- $a
# echo ${1}_01.${2}
FILE_Z66_ALPHA_01.txt
#unset IFS