move-if-change

   1 #!/bin/sh
   2 # Like mv $1 $2, but if the files are the same, just delete $1.
   3 # Status is 0 if $2 is changed, 1 otherwise.
   4 if
   5 test -r $2
   6 then
   7 if
   8 cmp -s $1 $2
   9 then
  10 echo $2 is unchanged
  11 rm -f $1
  12 else
  13 mv -f $1 $2
  14 fi
  15 else
  16 mv -f $1 $2
  17 fi