Merge entries to a line-oriented key-value configuration file

merge.sh

#!/bin/sh
##
## by ooharak 2012.
##
## _merge_entries target_file < merge_file
##   update entries in target_file with merge_file.
function _merge_entries {
  local file=$1
  local entry
  while read entry ; do
    local head=`echo "$entry"|cut -b 1`
    if [ "$head" == "#" ]; then
      local key=`echo "$entry" | cut -b 2- | cut -d = -f 1`
      sed -i -e "s/^$key/#$key/g" $file
    else
      local key=`echo "$entry" | cut -d = -f 1`
      sed -i -e "s/^$key/#$key/g;\$a$entry" $file
    fi
  done
}

function _test {
  cat <<-EOF > test.txt
  salary=100
	empno=123
	name=john
	EOF
  _merge_entries test.txt <<-EOF
	salary=200
	#empno=
	deptno=456
	EOF
  cat <<-EOF > expected.txt
	#salary=100
	#empno=123
	name=john
	salary=200
	deptno=456
	EOF
  diff expected.txt test.txt && echo "TEST OK" || echo "TEST NG"
  rm -f test.txt expected.txt
}

_test