copies

#!/usr/bin/env bash

if [ "$#" -ne 3 ]; then
  echo "Usage: ./copies [source-file] [dest-dir] [seconds-between-checks]" >&2; exit 1
fi

SRC=$1
DEST=$2
SECS=$3


if ! [ -f "$SRC" ]; then
  echo "No source-file found at $SRC" >&2; exit 1
fi
BASE=`basename $SRC`

if ! [ -d "$DEST" ]; then
  echo "No dest-dir found at $DEST" >&2; exit 1
fi

RE='^[0-9]+$'
if ! [[ $SECS =~ $RE ]]; then
   echo "seconds-between-copies not a number" >&2; exit 1
fi


echo "Copying new versions of $SRC to $DEST/[timestamp].$SRC every $SECS seconds."
echo "Use CTRL-C to stop."
echo

LAST=""
for (( ; ; ))
do
   STAMP=`date -u +"%Y-%m-%d.%H-%M-%S."`
   STAMPED_DEST="$DEST/$STAMP$BASE"

   if [ -z "$LAST" ] || ! $(cmp --silent "$SRC" "$LAST"); then
     echo "Changed: cp $SRC $STAMPED_DEST"
     cp $SRC $STAMPED_DEST
     LAST=$STAMPED_DEST
   else
    echo "Unchanged"
   fi

   sleep $SECS
done