golang/go · error

missing command

Error message

missing command

What it means

Thrown at the end of parse() when the line produced prefixes, conditions, arguments, or a background marker but no command name (cmd.name == ""). A line that is entirely blank or a comment returns (nil, nil); a line that has modifiers but no actual command is a syntax error. The guard checks cmd.want, cmd.conds, cmd.rawArgs, and cmd.background.

Source

Thrown at src/cmd/internal/script/engine.go:452

				i++ // skip over second ' before next iteration
				continue
			}
			// ending a quoted chunk
			rawArg = append(rawArg, argFragment{s: line[start:i], quoted: true})
			start = i + 1
			quoted = false
			continue
		}
		// found character worth saving; make sure we're saving
		if start < 0 {
			start = i
		}
	}

	if cmd.name == "" {
		if cmd.want != "" || len(cmd.conds) > 0 || len(cmd.rawArgs) > 0 || cmd.background {
			// The line contains a command prefix or suffix, but no actual command.
			return nil, errors.New("missing command")
		}

		// The line is blank, or contains only a comment.
		return nil, nil
	}

	if n := len(cmd.rawArgs); n > 0 {
		last := cmd.rawArgs[n-1]
		if len(last) == 1 && !last[0].quoted && last[0].s == "&" {
			cmd.background = true
			cmd.rawArgs = cmd.rawArgs[:n-1]
		}
	}
	return cmd, nil
}

// expandArgs expands the shell variables in rawArgs and joins them to form the
// final arguments to pass to a command.

View on GitHub (pinned to b6b368adc5)

Solutions

1. Add the command after the prefix/condition: `! nonexistent-cmd` not `! `.
2. Remove orphan prefixes/conditions/arguments if no command is intended (a truly blank line is fine).
3. Re-check that the command name was not accidentally quoted into a different token position.

Example fix

// before
! 
# -> missing command

// after
! nonexistent-binary arg

// A line must have a command name if it carries any prefix/cond/arg/&.
func hasCommand(line string) bool {
    t := strings.TrimSpace(line)
    // strip leading ! ? and [cond] tokens
    for strings.HasPrefix(t, "!") || strings.HasPrefix(t, "?") || (strings.HasPrefix(t, "[") && strings.Contains(t, "]")) {
        if strings.HasPrefix(t, "[") {
            t = strings.TrimSpace(t[strings.Index(t, "]")+1:])
        } else {
            t = strings.TrimSpace(t[1:])
        }
    }
    return t != "" && t != "&"
}

func isMissingCommand(err error) bool {
    return err != nil && err.Error() == "missing command"
}

// Lint script lines so any prefix/condition/& is followed by a real command.

When it happens

Trigger: A script line like `! ` (negation prefix but no command), `[cond]` alone, `? ` with nothing after, or a trailing `&` background marker on an otherwise empty line, or arguments supplied without a command name.

Common situations: Script-test author writes a prefix expecting to continue on the same line and forgets the command, or deletes the command while leaving a condition/prefix during editing.

Related errors

• duplicated '!' or '?' token
• empty condition
• empty command
• unterminated quoted argument
• syntax error

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/1935edaf0e8c048f. Report an issue: GitHub.