caddyserver/caddy · error

fmt does not support multiple files %s %s

Error message

fmt does not support multiple files %s %s

What it means

Error "fmt does not support multiple files %s %s" thrown in caddyserver/caddy.

Source

Thrown at cmd/commandfuncs.go:689

	if err != nil {
		return caddy.ExitCodeFailedStartup, fmt.Errorf("decoding config: %v", err)
	}

	err = caddy.Validate(cfg)
	if err != nil {
		return caddy.ExitCodeFailedStartup, err
	}

	fmt.Println("Valid configuration")

	return caddy.ExitCodeSuccess, nil
}

func cmdFmt(fl Flags) (int, error) {
	configFile := fl.Arg(0)
	configFlag := fl.String("config")
	if (len(fl.Args()) > 1) || (configFlag != "" && configFile != "") {
		return caddy.ExitCodeFailedStartup, fmt.Errorf("fmt does not support multiple files %s %s", configFlag, strings.Join(fl.Args(), " "))
	}
	if configFile == "" && configFlag == "" {
		configFile = "Caddyfile"
	} else if configFile == "" {
		configFile = configFlag
	}
	// as a special case, read from stdin if the file name is "-"
	if configFile == "-" {
		input, err := io.ReadAll(os.Stdin)
		if err != nil {
			return caddy.ExitCodeFailedStartup,
				fmt.Errorf("reading stdin: %v", err)
		}
		fmt.Print(string(caddyfile.Format(input)))
		return caddy.ExitCodeSuccess, nil
	}

	input, err := os.ReadFile(configFile)

View on GitHub (pinned to 50e54ee279)

Solutions

1. Run 'caddy fmt' on one file at a time instead of passing multiple files.

When it happens

Trigger: Thrown at cmd/commandfuncs.go:689 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of caddyserver/caddy@50e54ee279 (2026-08-15). Data as JSON: /api/errors/15c564c597640553. Report an issue: GitHub.