fetch target required, oldest, newest, config, or a number

Error message

fetch target required, oldest, newest, config, or a number

What it means

`peer channel fetch` takes a positional target argument saying which block to fetch: 'oldest', 'newest', 'config', or a block number. If no positional argument is present, the command cannot determine what to fetch and errors immediately.

Source

Thrown at internal/peer/channel/fetch.go:43

		Use:   "fetch <newest|oldest|config|(number)> [outputfile]",
		Short: "Fetch a block",
		Long:  "Fetch a specified block, writing it to a file.",
		RunE: func(cmd *cobra.Command, args []string) error {
			return fetch(cmd, args, cf)
		},
	}
	flagList := []string{
		"channelID",
		"bestEffort",
	}
	attachFlags(fetchCmd, flagList)

	return fetchCmd
}

func fetch(cmd *cobra.Command, args []string, cf *ChannelCmdFactory) error {
	if len(args) == 0 {
		return fmt.Errorf("fetch target required, oldest, newest, config, or a number")
	}
	if len(args) > 2 {
		return fmt.Errorf("trailing args detected")
	}
	// Parsing of the command line is done so silence cmd usage
	cmd.SilenceUsage = true

	// default to fetching from orderer
	ordererRequired := OrdererRequired
	peerDeliverRequired := PeerDeliverNotRequired
	if len(strings.Split(common.OrderingEndpoint, ":")) != 2 {
		// if no orderer endpoint supplied, connect to peer's deliver service
		ordererRequired = OrdererNotRequired
		peerDeliverRequired = PeerDeliverRequired
	}
	var err error
	if cf == nil {
		cf, err = InitCmdFactory(EndorserNotRequired, peerDeliverRequired, ordererRequired)

View on GitHub (pinned to 2736b63f8f)

Solutions

Provide the target as the first positional arg: peer channel fetch config <output.block> -c <channel> -o <orderer:port>.
Check flag ordering so flags don't consume the positional argument.
Verify shell quoting so the arg isn't lost to variable expansion.

Example fix

// before
peer channel fetch -c mychannel -o orderer:7050 newest.block
// after
peer channel fetch newest newest.block -c mychannel -o orderer:7050

Defensive patterns

Strategy: validation

Validate before calling

if [ $# -lt 1 ]; then echo "usage: peer channel fetch <oldest|newest|config|N> <outfile> -c <channel>" >&2; exit 1; fi
peer channel fetch "$@"

Type guard

function isValidFetchTarget(t) { return ['oldest','newest','config'].includes(t) || /^[0-9]+$/.test(t); }

Prevention

Always give the fetch target as the first positional arg.
Put flags after positional args to avoid confusion.
Share a usage wrapper for peer channel fetch.

When it happens

Trigger: Running `peer channel fetch` with zero positional args, e.g. `peer channel fetch -c mychannel config.block -o orderer:7050` where the target was given as a flag value instead of a positional arg.

Common situations: Misplaced flags swallowing the positional argument; copying an example that used a different CLI layout; shell splitting issues dropping the argument.

Understand the failure class

Background: "--flag is required" and "must specify" CLI errors: how missing-required-flag validation works and how to fix it — this error's family across 20 libraries.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/7007fc73265a7c4e. Report an issue: GitHub.