#!/bin/bash

for FILE_PATH; do
    # read first 20 bytes from file and exctract 11th and 12th bytes as hexadecimal value:
        HEAD_FLAGS="0x$(od -x -N20 "$FILE_PATH" | awk 'NR=1{print $7;exit}')"
        VOLUME_FLAG="0x0001"
        FIRST_FLAG="0x0100"

        if [ $(($HEAD_FLAGS&$VOLUME_FLAG)) -ne 0 ]; then # is volume
                if [ $(($HEAD_FLAGS&$FIRST_FLAG)) -ne 0 ]; then # is first volume
                        echo "$FILE_PATH is the first volume"
                else
                        echo "$FILE_PATH is NOT the first volume"
                fi
        else # is regular, single rar archive
                echo "$FILE_PATH is a regular, single RAR-file"
        fi
done