int tid, beg, end;
bam_parse_region(in->header, argv[i], &tid, &beg, &end); // parse a region in the format like `chr2:100-200'
if (tid < 0) { // reference name is not found
int tid, beg, end;
bam_parse_region(in->header, argv[i], &tid, &beg, &end); // parse a region in the format like `chr2:100-200'
if (tid < 0) { // reference name is not found