#!/bin/sh

if [ $# -lt 1 -o "$1" != "${1#-}" ]; then
  cat <<EOF
usage: $0 sed_expression [file [...]]

examples:

$ bsed 's/#include "..\//#include "/' foo/*.[ch]

   changes all #include "../ to #include "

$ bsed 's/VERSION/0.1/g' install.sh

   changes all VERSION strings to 0.1 in install.sh

$ find . -name '*.java' | xargs bsed 's/^package com\.firsthop\.foo/package com.firsthop.bar/'

   changes all java files below this directory belonging to package
   com.firsthop.foo to com.firsthop.bar. Remember that you need to
   rename the "foo" directory in com/firsthop/ to "bar" yourself.

EOF
  exit 1
fi

s="$1"
shift

sed "$s" < /dev/null || exit 1

for i in "$@" ; do
  if [ -f "$i" ]; then
    rm -f ..bsed_tmp.. 2>/dev/null
    sed "$s" < "$i" > ..bsed_tmp..
    diff -q -- "$i" ..bsed_tmp.. > /dev/null || {
	cat ..bsed_tmp.. > "$i"
    }
    rm ..bsed_tmp..
  fi
done