hashicorp/nomad · error

stdin already consumed

Error message

stdin already consumed

What it means

KVBuilder allows reading from stdin at most once per invocation. Once '-' has been consumed (the unexported stdin flag is set), a second '-' argument triggers this error. It prevents ambiguous double-reads of a non-seekable stream.

Source

Thrown at command/var.go:213

	}

	// Empty strings are fine, just ignored
	if raw == "" {
		return nil
	}

	// Split into key/value
	parts := strings.SplitN(raw, "=", 2)

	// If the arg is exactly "-", then we need to read from stdin
	// and merge the results into the resulting structure.
	if len(parts) == 1 {
		if raw == "-" {
			if b.Stdin == nil {
				return fmt.Errorf("stdin is not supported")
			}
			if b.stdin {
				return fmt.Errorf("stdin already consumed")
			}

			b.stdin = true
			return b.addReader(b.Stdin)
		}

		// If the arg begins with "@" then we need to read a file directly
		if raw[0] == '@' {
			f, err := os.Open(raw[1:])
			if err != nil {
				return err
			}
			defer f.Close()

			return b.addReader(f)
		}
	}

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Pass '-' only once per command invocation; combine remaining vars as explicit key=value pairs
2. Merge all JSON input into a single stdin payload read by the one '-'
3. If multiple stdin reads are genuinely needed, construct a new KVBuilder with a fresh Stdin reader

Example fix

// before
b.Add("-", "-")
// after
b.Add("-")
b.Add("otherkey=othervalue")

if n := strings.Count(strings.Join(args, " "), "\"-\"") + countExactDashes(args); n > 1 {
	// reject: stdin can only be consumed once
}

When it happens

Trigger: Passing '-' twice to KVBuilder.Add, e.g. Add("-", "-") or two '-var -' flags in one command, after the first '-' successfully consumed Stdin.

Common situations: Shell scripts piping one JSON blob but specifying '-var -' multiple times; loops that append '-var -' per variable when the intent was 'key=-' per pair.

Related errors

• Invalid key value pair for topic: %s
• invalid key/value pair %q: %w
• stdin is not supported
• format must be key=value
• error reading file: %w

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/6cbab969a3b6a78c. Report an issue: GitHub.