copy-if-change

#!/bin/sh
#
# Like cp $1 $2, but if the files are the same, do NOTHING.
# Status is 0 if $2 is changed, 1 otherwise.

if test -r $2; then
  if cmp $1 $2 > /dev/null; then
    echo $2 is unchanged
  else
    cp -f $1 $2
  fi
else
  cp $1 $2
fi