root@ubuntu:~/test# cat re
#!/bin/bash
# code by thatday
#
ls -l $1 | grep ^[^d] | awk '{print $9}'| while read line; do
do=`echo $line | grep $2`

if [ ! "$do" = "" ]; then
   newname=`echo $line | sed 's/'$2'/'$3'/g'`
   echo "rename $line to $newname ..."
   mv $1/$line $1/$newname
fi
done

root@ubuntu:~# chmod +x re


root@ubuntu:~# ls -l test/
total 4
-rw-r--r-- 1 root root    0 Jul  9 13:45 20070808jjj
-rw-r--r-- 1 root root    0 Jul  9 13:45 20070809abc
-rw-r--r-- 1 root root    0 Jul  9 13:45 aaa20070809bb
drwxr-xr-x 2 root root 4096 Jul  9 12:05 bak
-rw-r--r-- 1 root root    0 Jul  9 13:45 ccccc200708091
-rw-r--r-- 1 root root    0 Jul  9 13:45 dddd20070809aj

root@ubuntu:~# ./re test/ 20070809 20070810
rename 20070809abc to 20070810abc ...
rename aaa20070809bb to aaa20070810bb ...
rename ccccc200708091 to ccccc200708101 ...
rename dddd20070809aj to dddd20070810aj ...
root@ubuntu:~# ls test/
20070808jjj  20070810abc  aaa20070810bb  bak  ccccc200708101  dddd20070810aj