[UNIX/LINUX] Shell Script for changing all string in a directory recursivly!

A Shell Script For Changing Oldstring to NewString in a directory recursively.
This code, which we will call ach(All Change), finds all files whose extension is one of .c, .h, .s .cpp and contain the OldString.  And It Chanes OldString to New String in one breath.
It's very useful!

USAGE:
$ach oldstring newstring

REQUIREMENTS:
vim6.0 or above
sed
grep

CODE:
#!/bin/sh

# Check parameters
if [ "$#" -ne 2 ]
then
  echo "All Change Oldstring to Newstring in a directory recursively"
  echo "usage:ach Oldstring Newstring"
  exit
fi

if [ -f ./vim.scr ]
then
  echo "vim.scr already exists!"
  rm -rf ./vim.scr
  echo "vim.scr removed!"
  exit 1
else
  touch ./vim.scr
  echo ":%s,\<$1\>,$2,g">> vim.scr
  echo ":wq">> vim.scr
  find ./ \( -name '*.c' -o -name '*.h' -o -name '*.s' -o -name '*.cpp' \) -print > allfiles
  temp1=`cat allfiles`
  for files in `echo $temp1`
  do
      grep -l "\<$1\>" $files /dev/null | sed 's/.*/vim & -s vim.scr/' >> tmpfiles
  done
  if [ -s tmpfiles ]
  then
      sh tmpfiles
  else
      echo "ach:No file to chage"
  fi
  rm -rf ./vim.scr
  rm -rf ./tmpfiles
  rm -rf ./allfiles
fi