# Show command usage

Put the `-h` output of a Go command in a page, so that the page changes when a flag changes.

<!-- site:editor -->

<!-- docgen:code file=internal/cli/testdata/repo/cmd/tool/main.go symbol=main -->

``` go
func main() {
    n := flag.Int("n", 3, "how many lines to print")
    flag.Parse()
    for i := 0; i < *n; i++ {
        fmt.Println(i)
    }
}
```

<!-- /docgen:code -->

<!-- docgen:docgen root=internal/cli/testdata/repo module=v2 page=docs/machines/guide-usage.md -->

#### Before

    # Flags

    <!-- docgen:usage cmd=cmd/tool -->
    <!-- /docgen:usage -->

#### After

    # Flags

    <!-- docgen:usage cmd=cmd/tool -->
    ```text
    Usage of tool:
      -n int
            how many lines to print (default 3)
    ```
    <!-- /docgen:usage -->

<!-- /docgen:docgen -->

<!-- /site:editor -->

The directory is relative to the repository root. A build failure, a crash, or output with no usage is an error.

With `args=`, docgen runs the command with other arguments, such as `args="help config"` for a help command. The output must still hold a usage line or a flag line.

For details, see [`docgen:usage`](../reference/markers.md#docgenusage).