colorize() -- sometimes you need more than grep --color

# colorize [-c ANSI] pattern
#
# Colorize text matching pattern with ANSI sequence (default is `31;1' for red-
# bold). Non-matching lines are printed as-is.
#
colorize()
{
    local OPTIND=1 OPTARG flag
    local ansi_color=

    while getopts c: flag; do
        case "$flag" in
        c) ansi_color="$OPTARG" ;;
        esac
    done
    shift $(( $OPTIND - 1 ))

    awk -v color="${ansi_color:-31;1}" -v pattern="$1" '
        (match($0, pattern) && $0 = sprintf("%s%c[%sm%s%c[0m%s",
            substr($0, 0, RSTART - 1), 27, color,
            substr($0, RSTART, RLENGTH), 27,
            substr($0, RSTART + RLENGTH))) || 1
    ' # END-QUOTE
}