Swaps two files.

swap.sh

#!/bin/sh

if test $# -ne 2
then
  echo "Usage: swap <filename> <filename>"
  exit 1
fi

if test ! -w "$1"
then
  echo "$1 is not writable"
  exit 2
fi

if test ! -w "$2"
then
  echo "$2 is not writable"
  exit 2
fi

tempfoo=`basename $0`
TEMPFILE=`mktemp -t ${tempfoo}`
if [ $? -ne 0 ]
then
  echo "Could not create temporary file"
  exit 3
fi

mv "$1" "$TEMPFILE"
mv "$2" "$1"
mv "$TEMPFILE" "$2"

exit 0