Global flags

Every flag below can appear before OR after the subcommand — go-udap -v read MAC and go-udap read -v MAC are equivalent.

Output formatsCopy Anchor Link

--format/-o selects how a command writes its result to stdout: text (the default), json or csv. --json is shorthand for --format json. Names must be lowercase and exact; anything else is a usage error (exit 2). Giving --json together with --format is a usage error, even when they agree.

Only stdout changes. Errors, warnings, progress and logs stay as plain text on stderr, and the exit code still reports failure.

• JSON is compact: one value per invocation and a trailing newline. A list is a bare array and anything else is an object. Every key is always present, with null for an absent value.
• CSV follows RFC 4180, always starts with a header row, and writes null as an empty cell.
• Empty results give [] for a list or {} for a parameter map in JSON, and the header row alone in CSV.

Commands that support the format flags: discover (with or without --info), info, getip, interfaces, read, get, set, --version and --build-info. A format flag on a command that writes no data output, such as reboot, is a usage error (exit 2). --help always wins: go-udap reboot --json --help prints help.

JSON keys and CSV columns are a stable contract, documented on each command's page. Removing or renaming one is a breaking change and only happens in a major version. Adding one is not breaking.

--versionCopy Anchor Link

$ go-udap --version
go-udap 3.0.0
$ go-udap --version --json
{"name":"go-udap","version":"3.0.0"}
$ go-udap --version -o csv
name,version
go-udap,3.0.0

--build-infoCopy Anchor Link

Version plus build metadata read from the binary: commit, commit time, whether the working tree was modified, Go version, OS and architecture. A field is null when the build didn't record it, for example a go run build has no commit. The text form omits absent fields.

$ go-udap --build-info
go-udap 3.0.0
Commit:      db37553ed89bdfcf9bad1781232a338c4c3cc0d9
Commit time: 2026-10-09T13:43:01Z
Modified:    false
Go version:  go1.27.2
OS:          darwin
Arch:        arm64

JSON keys, in order: name, version, commit, commit_time, modified (a boolean), go_version, os, arch. CSV uses the same names as its header row.

--verbose with --version or --build-info is a usage error (exit 2).

Multi-interface behaviour (--bind-interface / --all-interfaces)Copy Anchor Link

Discovery only emits broadcasts on the kernel's default-route NIC by default. On a multi-homed laptop (Wi-Fi + Ethernet both up), if the Squeezebox is on the non-default subnet you'll see zero devices.

--bind-interface NAME forces UDAP traffic out a specific NIC via IP_BOUND_IF (macOS) / SO_BINDTODEVICE (Linux). --all-interfaces sends concurrently on every NIC.

The singular form is spelled --bind-interface (not --interface) because --interface 0|1 is also a per-parameter flag on set — it configures the device's NVRAM interface byte (0 = wireless, 1 = wired). Two unrelated concepts share the word, so the local-NIC binding flag gets the more specific name.

See How to discover on a multi-NIC laptop for usage, and Multi-NIC discovery for the underlying mechanics.