Audio: let `audio-devices <device>` write the config

The audio-devices command only listed. Give it an optional positional
argument: with none it lists as before; with a device name (or
case-insensitive fragment) it writes that into [audio] device in
crabidy-server.toml and then lists, so the same command both configures
and confirms (the chosen device is marked with *). If the fragment
matches no current output device it still writes but warns, mirroring
the server's startup fallback -- so a typo is caught here, not as silent
output.

Plumbing: AudioDevices carries an AudioDevicesArgs { device: Option }
on both `crabidy-server` and `cbd`; cli::audio_devices takes the option
and, when set, loads/updates/stores the settings via the existing
ServerSettings writer. README shows the set form.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -171,17 +171,24 @@ Audio output devices (* = selected by the current config):
     ...
 ```
 
-Then pin one in `crabidy-server.toml` — the value is matched
+Then pin one by passing it to the same command — the value is matched
 case-insensitively as a substring of the name, so a memorable fragment is
 enough — and restart the server:
 
+```console
+$ crabidy-server audio-devices Headphones
+Set [audio] device = "Headphones" in .../crabidy-server.toml
+```
+
+That writes `[audio] device` for you; you can also edit it by hand:
+
 ```toml
 [audio]
 device = "Headphones"
 ```
 
-If the name matches nothing, the server logs a warning and falls back to
-the system default.
+If the name matches nothing, both the command and the server warn, and the
+server falls back to the system default.
 
 ## Command line
 

cbd-cli/src/lib.rs

@@ -179,6 +179,15 @@ pub struct CompletionsArgs {
     pub shell: clap_complete::Shell,
 }
 
+/// `audio-devices [device]`: list the output devices, or — with `device` — set
+/// `[audio] device` in `crabidy-server.toml`.
+#[derive(Debug, Args)]
+pub struct AudioDevicesArgs {
+    /// A name (or case-insensitive fragment) of an output device to write into
+    /// `[audio] device`. Omit to just list the available devices.
+    pub device: Option<String>,
+}
+
 /// Subcommands of `crabidy-server`.
 #[derive(Debug, Subcommand)]
 pub enum ServerCommand {
@@ -195,8 +204,8 @@ pub enum ServerCommand {
     /// Playback / global operations against a running server.
     #[command(subcommand)]
     Global(GlobalCmd),
-    /// List the audio output devices (to pick `[audio] device`).
-    AudioDevices,
+    /// List audio output devices, or set `[audio] device` if one is given.
+    AudioDevices(AudioDevicesArgs),
     /// Print a shell completion script.
     Completions(CompletionsArgs),
 }
@@ -251,8 +260,8 @@ pub enum CbdCommand {
     Queue(QueueCmd),
     #[command(subcommand)]
     Global(GlobalCmd),
-    /// List the audio output devices (to pick `[audio] device`).
-    AudioDevices,
+    /// List audio output devices, or set `[audio] device` if one is given.
+    AudioDevices(AudioDevicesArgs),
     /// Print a shell completion script.
     Completions(CompletionsArgs),
 }

cbd/src/main.rs

@@ -92,7 +92,7 @@ async fn run_command(
     match command {
         CbdCommand::Guard(args) => server_cli::guard(args).await,
         CbdCommand::Scan(args) => server_cli::scan(args).await,
-        CbdCommand::AudioDevices => server_cli::audio_devices(),
+        CbdCommand::AudioDevices(args) => server_cli::audio_devices(args.device),
         CbdCommand::Auth(args) => {
             let password = args
                 .password

crabidy-server/src/cli.rs

@@ -102,12 +102,43 @@ pub async fn guard(args: GuardArgs) -> Result<(), Box<dyn Error>> {
     Ok(())
 }
 
-/// `audio-devices`: list the available audio output devices so the user can
-/// choose one for `[audio] device` in `crabidy-server.toml`. Marks the device
-/// the current config selects, using the same case-insensitive substring match
-/// the server applies at startup. Fixes the common Raspberry Pi case where the
-/// default device is HDMI and audio plays but is silent on the jack/DAC.
-pub fn audio_devices() -> Result<(), Box<dyn Error>> {
+/// `audio-devices [device]`: with no argument, list the available audio output
+/// devices so the user can choose one for `[audio] device` in
+/// `crabidy-server.toml`, marking the device the current config selects (same
+/// case-insensitive substring match the server applies at startup). With a
+/// `device` argument, write it into `[audio] device` and then list — so one
+/// command both configures and confirms. Fixes the common Raspberry Pi case
+/// where the default device is HDMI and audio plays but is silent on the
+/// jack/DAC.
+pub fn audio_devices(select: Option<String>) -> Result<(), Box<dyn Error>> {
+    // Setting a device needs a writable config dir; listing tolerates its
+    // absence.
+    if let Some(device) = select {
+        let dir = config_dir()?;
+        let mut settings = ServerSettings::load(&dir)?;
+        settings.audio.device = Some(device.clone());
+        settings.store(&dir)?;
+        println!(
+            "Set [audio] device = \"{device}\" in {}",
+            dir.join(crate::settings::SETTINGS_FILE).display()
+        );
+        // The server matches the same way; warn on a fragment that currently
+        // resolves to nothing so a typo is caught here, not as silent output.
+        let needle = device.to_lowercase();
+        let names = audio_player::output_device_names();
+        if !names.is_empty()
+            && !names
+                .iter()
+                .any(|name| name.to_lowercase().contains(&needle))
+        {
+            eprintln!(
+                "warning: no current output device name contains \"{device}\"; the server \
+                 will fall back to the system default until one matches"
+            );
+        }
+        println!("Restart the server for it to take effect.\n");
+    }
+
     let dir = config_dir().ok();
     let configured = dir
         .as_deref()

crabidy-server/src/main.rs

@@ -41,7 +41,7 @@ async fn run_command(
     match command {
         ServerCommand::Guard(args) => cli::guard(args).await,
         ServerCommand::Scan(args) => cli::scan(args).await,
-        ServerCommand::AudioDevices => cli::audio_devices(),
+        ServerCommand::AudioDevices(args) => cli::audio_devices(args.device),
         ServerCommand::Library(cmd) => {
             cbd_cli::run_remote(&cli::connection(remote), RemoteCmd::Library(cmd)).await
         }