#!/bin/sh

if [ ! -f "$1" ]
then
  echo "'$1' nie istnieje lub nie jest zwykłym plikiem"
  exit
fi

if [ ! -x "$1" ]
then
  chmod +x "$1"
fi

FIRSTLINE="$(head -n1 "$1")"
if [ "$FIRSTLINE" != "#!/bin/sh" ]
then
  TEMPFILE="$(mktemp -p. || mktemp)"
  echo '#!/bin/sh' > "$TEMPFILE"
  cat "$1" >> "$TEMPFILE"
  chmod --reference="$1" "$TEMPFILE"
  touch --reference="$1" "$TEMPFILE"
  mv "$TEMPFILE" "$1"
fi