Use grep to print lines between two regular expressions

grep_between.sh

function grep_between () {
    if [ -z $1 -o -z $2 -o -z $3 ]; then
        echo "Usage:\ngrep_between 'starting regex' 'ending regex' file1 [file2 file3 ...]"
        exit 2
    fi

    startregex=$1
    endregex=$2

    for i in ${@:3}; do
        start="$(grep -n -m1 "$startregex" $i)"
        if [ -n "$start" ]; then
            startl="$(cut -d':' -f1 <<< $start)"
            end="$(tail -n +$(( $startl + 1 )) $i | grep -n -m1 "$endregex")"
            if [ -n "$end" ]; then
                endl="$(( $(cut -d':' -f1 <<< $end) + $startl -1 ))"
                echo "\n--\n$i:"
                sed -n -e "${startl},${endl}p" $i
            else
                tail -n +$startl $i
            fi;
        fi;
    done
}