```sh
samtools flagstat --help
```
Usage: samtools flagstat [options] <in.bam>
      --input-fmt-option OPT[=VAL]
               Specify a single input file format option in the form
               of OPTION or OPTION=VALUE
  -@, --threads INT
               Number of additional threads to use [0]
      --verbosity INT
               Set level of verbosity
  -O, --output-fmt FORMAT[,OPT[=VAL]]...
               Specify output format (json, tsv)