def read_snp_position_list(snp_list_file_path):
    """Read list of snp positions across all samples from the snplist.txt.

    Args:
        snp_list_file_path : path to snplist file to be written

    Returns:
        snp_list  : sorted list of tuple(str(CHROM), int(POS))
    """
    snp_list = list()
    with open(snp_list_file_path, 'r') as snp_list_file_object:
        for line in snp_list_file_object:
            chrom, pos = line.split()[0:2]
            snp_list.append((chrom, int(pos)))
    return snp_list
