move-if-change

   1 #!/bin/sh
   2 if
   3 test -r $2
   4 then
   5 if
   6 cmp $1 $2 > /dev/null
   7 then
   8 echo $2 is unchanged
   9 rm -f $1
  10 else
  11 mv -f $1 $2
  12 fi
  13 else
  14 mv -f $1 $2
  15 fi