#!/bin/sh

command=$0
substs=

while [ -n "$4" ]; do
  substs=${substs}" -e 's:$1:$2:g'"
  shift 2
done

if [ -n "$3" -o -z "$substs" ]; then
  echo "Usage: $command text1 subst1 text2 subst2 ... infile outfile"
  exit 1
fi

# Override shell clobbering
/bin/rm -f $2

eval "sed $substs < '$1' > '$2'"