What causes "Invalid value for "-in"; valid values are [hcl, json]" in hashicorp/nomad?

Use -in=hcl or -in=json (lowercase)

Invalid value for "-in"; valid values are [hcl, json]

Error message

Invalid value for "-in"; valid values are [hcl, json]

What it means

Returned by VarPutCommand.validateInputFlag when the -in flag (or a file extension that could not be inferred) is neither "hcl" nor "json". The sentinel errInvalidInFormat marks an unusable input format for the variable payload.

Source

Thrown at command/var_put.go:595

func (c *VarPutCommand) setParserForFileArg(arg string) error {
	switch filepath.Ext(arg) {
	case ".json":
		c.inFmt = "json"
	case ".hcl":
		c.inFmt = "hcl"
	default:
		return fmt.Errorf("Unable to determine format of %s; Use the -in flag to specify it.", arg)
	}
	return nil
}

func (c *VarPutCommand) validateInputFlag() error {
	switch c.inFmt {
	case "hcl", "json":
		return nil
	default:
		return errors.New(errInvalidInFormat)
	}
}

func (c *VarPutCommand) validateOutputFlag() error {
	if c.outFmt != "go-template" && c.tmpl != "" {
		return errors.New(errUnexpectedTemplate)
	}
	switch c.outFmt {
	case "none", "json", "hcl", "table":
		return nil
	case "go-template":
		if c.tmpl == "" {
			return errors.New(errMissingTemplate)
		}
		return nil
	default:
		return errors.New(errInvalidOutFormat)
	}

View on GitHub (pinned to 482b49bf1a)

Solutions

Use -in=hcl or -in=json (lowercase)
Convert yaml/toml input to json or hcl before invoking
Fix spelling/case of the -in value

Example fix

// before
vault kv put -in=yaml secret/foo @spec.yaml
// after
vault kv put -in=json secret/foo @spec.json

Defensive patterns

Strategy: validation

Validate before calling

if inFmt != "hcl" && inFmt != "json" {
	return fmt.Errorf("invalid -in %q; must be hcl or json", inFmt)
}

Try / catch

if err := cmd.validateInputFlag(); err != nil {
	if strings.Contains(err.Error(), "Invalid value for \"-in\"") {
		// convert input to json/hcl and retry
	}
	return err
}

Prevention

Only hcl and json are accepted; convert yaml/toml beforehand
Lowercase the value in wrappers
Use shell completion to avoid typos

When it happens

Trigger: Running `vault kv put -in=yaml|toml|text ...` or a misspelled value like -in=HCL.

Common situations: Assuming yaml input is supported; case-sensitivity mistakes; scripts generated with wrong format names.

Understand the failure class

Background: "unknown output mode", "invalid value for flag", "expects true/false": fixing invalid flag value errors in CLI tools — this error's family across 24 libraries.

Related errors

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/f183a536a78cbe00. Report an issue: GitHub.