fgrep in sh (maybe bashisms)

fgrep.sh

fgrep() {
    # Parse options
    local dashv=0 dashq=0 dashx=0 opt= OPTIND=1
    local usage='
                echo "Usage: fgrep [-vqx] string" >&2;
                return 1;
            '
    while getopts "vqx" opt; do
        case "$opt" in
            'v')  dashv=1 ;;
            'q')  dashq=1 ;;
            'x')  dashx=1 ;;
            '?')  eval "$usage" ;;
        esac
    done
    shift $(( OPTIND - 1 ))
    if [ $# != 1 ]; then
        eval "$usage"
    fi
    # Do matching
    local line= matched= found=0
    while read line; do
        case "$line" in
            "$1")    let 'matched = !dashv' ;;
            *"$1"*)  let 'matched = (dashx ? dashv : !dashv)' ;;
            *)       let 'matched = dashv' ;;
        esac
        if [ $matched = 1 ]; then
            found=1
            if [ $dashq = 1 ]; then
                break
            else
                echo "$line"
            fi
        fi
    done
    return $(( ! found ))
}