docker/cli · error

bad format: %s

Error message

bad format: %s

What it means

Error "bad format: %s" thrown in docker/cli.

Source

Thrown at opts/weightdevice.go:18

package opts

import (
	"fmt"
	"strconv"
	"strings"

	"github.com/moby/moby/api/types/blkiodev"
)

// ValidatorWeightFctType defines a validator function that returns a validated struct and/or an error.
type ValidatorWeightFctType func(val string) (*blkiodev.WeightDevice, error)

// ValidateWeightDevice validates that the specified string has a valid device-weight format.
func ValidateWeightDevice(val string) (*blkiodev.WeightDevice, error) {
	k, v, ok := strings.Cut(val, ":")
	if !ok || k == "" {
		return nil, fmt.Errorf("bad format: %s", val)
	}
	// TODO(thaJeztah): should we really validate this on the client?
	if !strings.HasPrefix(k, "/dev/") {
		return nil, fmt.Errorf("bad format for device path: %s", val)
	}
	weight, err := strconv.ParseUint(v, 10, 16)
	if err != nil {
		return nil, fmt.Errorf("invalid weight for device: %s", val)
	}
	if weight > 0 && (weight < 10 || weight > 1000) {
		return nil, fmt.Errorf("invalid weight for device: %s", val)
	}

	return &blkiodev.WeightDevice{
		Path:   k,
		Weight: uint16(weight),
	}, nil
}

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at opts/weightdevice.go:18 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/1518ccdf87dbdef0.json. Report an issue: GitHub.