Use this bash script to destroy your config files!

update-config-val

#!/bin/bash

COMMENT_PREFIX=${COMMENT_PREFIX:="#"}
SEPARATOR=${SEPARATOR:="="}

in_place=no

function usage {
    echo "update-config-val: comment all lines beginning with <config-property> and insert a line at the end of the <file> with the format <config-property>$SEPARATOR<value>

Usage: update-config-val [OPTIONS] config-property value file

Options:
        -c PREFIX, --comment-prefix PREFIX  - Set the prefix to use when commenting out old values. defaults to '#'
        -s SEPARATOR, --separator SEPARATOR - Set the separator between property and value. defaults to '='
        -i, --in-place                      - Modify the file in place rather than printing the new file to stdout"

}

if [ $# -lt 3 ]; then
    usage
    exit 1
fi

while [ $# -gt 3 ]; do
    case $1 in
        -h|--help)
            usage
            exit 0
            ;;
        -s|--separator)
            SEPARATOR="$2"
            shift
            ;;
        -c|--comment-prefix)
            COMMENT_PREFIX="$2"
            shift
            ;;
        -i|--in-place)
            in_place=yes
            ;;
        *)
            echo "Unknown option: $1"
            usage
            exit 1
            ;;
    esac
    shift
done

property=$1
value=$2
file=$3

function new_file {
    sed "s/^$property.*/$COMMENT_PREFIX&/g" $file
    echo "$COMMENT_PREFIX Set on $(date)"
    echo "$property$SEPARATOR$value"
}

if [ $in_place = yes ]; then
    temp_file=$(mktemp "update-config-val.XXXXXX")
    new_file > $temp_file
    mv $temp_file $file
else
    new_file
fi