.
├── aclocal.m4
├── bgzf.c
├── bgzf.o
├── bgzip.c
├── bgzip.o
├── config.h
......
|── cram
│   ├── cram_codecs.c
│   ├── cram_codecs.h
│   ├── cram_codecs.o
......
├── header.c
├── header.h
├── header.o
......
├── hts.c
├── htsfile.c
├── htsfile.o
├── hts_internal.h
├── htslib
│   ├── faidx.h
│   ├── hfile.h
│   ├── hts_defs.h
│   ├── hts_endian.h
│   ├── hts.h
......

├── kstring.c
├── kstring.o
├── vcf.c
├── vcf.o
......

gcc -Wall -O3 -I ./htslib-1.10.2/htslib  -o vcf_parser01 vcf.c  vcf_parser01.c

vcf_parser01.c:(.text.startup+0x19): undefined reference to `hts_open'
vcf_parser01.c:(.text.startup+0x73): undefined reference to `hts_close'
/tmp/cc05JReL.o: In function `bcf_hdr_add_sample_len':
vcf.c:(.text+0x989): undefined reference to `hts_log'
/tmp/cc05JReL.o: In function `bcf_hdr_set_idx.isra.10':
vcf.c:(.text+0x116b): undefined reference to `hts_log'
vcf.c:(.text+0x11d5): undefined reference to `hts_resize_array_'
/tmp/cc05JReL.o: In function `bcf_subset_format.part.19':
vcf.c:(.text+0x18e5): undefined reference to `hts_realloc_or_die'
/tmp/cc05JReL.o: In function `bcf_hdr_format.constprop.30':
vcf.c:(.text+0x1e35): undefined reference to `ksprintf'
vcf.c:(.text+0x1e73): undefined reference to `ksprintf'
vcf.c:(.text+0x1ed3): undefined reference to `ksprintf'