move-if-change

   1 #!/bin/sh
   2 # Like mv $1 $2, but if the files are the same, just delete $1.
   3 # Status is zero if successful, nonzero otherwise.
   4
   5 usage="$0: usage: $0 SOURCE DEST"
   6
   7 case $# in
   8 2) ;;
   9 *) echo "$usage" >&2; exit 1;;
  10 esac
  11
  12 for arg in "$1" "$2"; do
  13   case $arg in
  14    -*) echo "$usage" >&2; exit 1;;
  15   esac
  16 done
  17
  18 if test -r "$2" && cmp -s "$1" "$2"; then
  19   rm -f "$1"
  20 else
  21   mv -f "$1" "$2"
  22 fi