Simple file renaming using a loop in shell

File renaming

#!/bin/sh

# 
# Create a list of all txt files
# Loop over all files
#  Extract name (split on '_')
#  Copy file to new extension (text)
#

files=`ls -l *.txt | awk '{print $9}'`

for f in ${files}
 do
   echo $f
   f_id=`echo $f | awk '{split($0,a,"_"); print a[1]}'`
   echo $f_id
   cp $f $f_id.text
 done