cp_if_different.sh

   1 #/bin/sh
   2 # Copy $SRC to $DST unless $DST already exists and has the same contents.
   3 SRC="$1"
   4 DST="$2"
   5
   6 if cmp -s "$SRC" "$DST" 2>/dev/null; then
   7     :
   8 else
   9     cp "$SRC" "$DST"
  10 fi