error parsing usage-threshold: invalid option '%s'

Error message

error parsing usage-threshold: invalid option '%s'

What it means

main validates the --usage-threshold flag, which must contain exactly two comma-separated numeric values (float percentages). If splitting on "," does not yield exactly two parts, the program prints "error parsing usage-threshold: invalid option '%s'" to stderr and exits with status 1.

Source

Thrown at main.go:325

	// validate availability thresholds
	availbilityThresholds := strings.Split(*availThreshold, ",")
	if len(availbilityThresholds) != 2 {
		fmt.Fprintln(os.Stderr, fmt.Errorf("error parsing avail-threshold: invalid option '%s'", *availThreshold))
		os.Exit(1)
	}
	for _, threshold := range availbilityThresholds {
		_, err = stringToSize(threshold)
		if err != nil {
			fmt.Fprintln(os.Stderr, "error parsing avail-threshold:", err)
			os.Exit(1)
		}
	}

	// validate usage thresholds
	usageThresholds := strings.Split(*usageThreshold, ",")
	if len(usageThresholds) != 2 {
		fmt.Fprintln(os.Stderr, fmt.Errorf("error parsing usage-threshold: invalid option '%s'", *usageThreshold))
		os.Exit(1)
	}
	for _, threshold := range usageThresholds {
		_, err = strconv.ParseFloat(threshold, 64)
		if err != nil {
			fmt.Fprintln(os.Stderr, "error parsing usage-threshold:", err)
			os.Exit(1)
		}
	}

	// print out warnings
	if *warns {
		for _, warning := range warnings {
			fmt.Fprintln(os.Stderr, warning)
		}
	}

	// detect terminal width

View on GitHub (pinned to 4636deb4a7)

Solutions

Supply exactly two comma-separated floats, e.g. --usage-threshold "80,95".
Remove stray characters/extra commas from the flag value.
Quote the argument in shell scripts to preserve the comma-separated format.

Example fix

// before
--usage-threshold 80
// after
--usage-threshold "80,95"

Defensive patterns

Strategy: validation

Validate before calling

parts := strings.Split(usageThreshold, ",")
if len(parts) != 2 {
	return fmt.Errorf("usage-threshold needs exactly 2 values")
}
for _, p := range parts {
	if _, err := strconv.ParseFloat(p, 64); err != nil { /* invalid */ }
}

Try / catch

if err := validateUsageThreshold(flag); err != nil {
	fmt.Fprintln(os.Stderr, err)
	os.Exit(1)
}

Prevention

Always pass two comma-separated numbers like "80,95".
Quote the flag value in shell scripts.
Use plain floats without % signs or units.

When it happens

Trigger: Running with --usage-threshold containing anything other than two comma-separated floats, e.g. "80", "", "80,90,100", or non-numeric tokens.

Common situations: Users pass a single percentage, separate values with spaces or semicolons instead of commas, or accidentally quote the flag value twice in shell.

Understand the failure class

Background: "Unknown argument", "Invalid value", and "must be one of": invalid CLI argument errors explained — this error's family across 35 libraries.

Related errors

AI-assisted analysis of muesli/duf@4636deb4a7 (2026-09-06). Data as JSON: /api/errors/c123a9da18232773. Report an issue: GitHub.