bar_daemon — A Daemon For Status Bars

A daemon that can be queried for specific values, and set values (With notifications for some), can also run as a listener which will be sent all of the values in JSON format whenever a value is updated (Certain values are polled, e.g battery, ram).

Notifies on the change of values, and can be queried for the icon of a particular entry, given its type and value.

Intended for use with a status bar, reduces the amount of values which need to be polled for.

Polled values can also be event-driven, but this currently has a high performance cost.

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bar_daemon is available on the Arch User Repository.

It can be installed via paru -S bar_daemon, or any other AUR package installation service.

Usage

Listen for changes/polled values

bar_daemon listen

Start daemon

bar_daemon daemon

Get Volume Percent

bar_daemon get volume percent
bar_daemon get v p
bar_daemon get vol per

Get Battery Time

bar_daemon get battery time
bar_daemon get bat time
bar_daemon get bat t

Get Battery Icon

bar_daemon get battery icon
bar_daemon get bat i

Set Fan Speed

bar_daemon set fan profile Balanced
bar_daemon set fanprofile profile next
bar_daemon set fan p prev

Get All (Responds with an Enum of all the tuples in JSON format)

bar_daemon get
bar_daemon get all

More Information

Use bar_daemon help or bar_daemon <COMMAND> help to get more info about usage

Config

By default the config file is located at .config/bar_daemon/config.toml, when the program is first run, if this file doesn't exist, the default config will be copied from /etc/bar_daemon/config.toml

Example Config

# Timeout for notification (in milliseconds)
notification_timeout = 1000

# Polling rate for polled values (in milliseconds)
polling_rate = 2000

Performance

This daemon is very performance light, The last few outputs of journalctl are as follows:

Consumed 4.181s CPU time over 25min 34.911s wall clock time, 15.7M memory peak. (0.262% CPU time)

Consumed 15.332s CPU time over 1h 31min 20.089s wall clock time, 7.2M memory peak. (0.280% CPU time)

Consumed 1min 30.738s CPU time over 3h 35min 2.319s wall clock time, 15.8M memory peak. (0.238% CPU time)

Consumed 35.898s CPU time over 1h 10min 6.469s wall clock time, 17.6M memory peak. (0.853% CPU time)

This means that the daemon only uses a few megabytes of memory and a tiny amount of CPU time, so it will not effect system performance in any noticable way.

Process Flow Diagram

Flow Diagram for bar_daemon daemon

flowchart TD
%% ---------- Startup ----------
  A[Systemd launches 'bar_daemon daemon'] --> B["init_logging()" called]

  subgraph INIT_LOGGING ["init_logging()"]
    C[Panic hook set]
    C --> D[tracing_subscriber created]
  end

  B --> C

  B --> E{"Parse CLI args with 'evaluate_cli()'"}
  E -- "[daemon]" --> F["do_daemon()" called]
  E -- "[listen]" --> AF[[... Handle 'listen' argument ...]]
  E -- "[get, ...]" --> AG[[... Handle 'get' argument ...]]
  E -- "[set, ...]" --> AH[[... Handle 'set' argument ...]]

%% ---------- Daemon Setup ----------
  subgraph DO_DAEMON ["do_daemon()"]
    G[Remove existing socket file]
    G --> H[Create new listener at 'SOCKET_PATH']
    H --> I["Spawn task to run handle_clients()"]
    I --> R[Spawn poller tasks]
    R --> AE[Run Listener Accept Loop]
  end

  F --> G

%% ---------- Handle Clients ----------
  subgraph HANDLE_CLIENTS ["handle_clients()"]
    J{SnapshotEvent or Shutdown}

    J -- SnapshotEvent --> K{Are there any clients?}

    K -- true --> L[Get monitored value in tuple format]
    L --> M[Convert tuple to JSON]
    M --> N[Update tuples Mutex]
    N --> O[Send JSON to all clients]
    O --> P[Remove dead clients]
    P --> J

    K -- false --> J
    J -- Shutdown Event --> Q["Close handle_clients()"]
  end

  I --> J

%% ---------- Listener Accept Loop ----------
  subgraph LISTENER_ACCEPT [Listener Accept Loop]
    S{Listener Receiver or Shutdown}

    S -- Connection --> T["Spawn handle_socket() for this listener"]
    S -- Shutdown Event --> AD[Remove socket file]
  end

  AE --> S

%% ---------- Client Socket Task ----------
  subgraph HANDLE_SOCKET ["handle_socket()"]
    U{Stream Read or Shutdown}

    U -- Stream Read --> V{Is stream buffer empty?}

    V -- true --> W["Close handle_socket()"]
    V -- false --> X[Convert bytes to DaemonMessage]

    X --> Y{Get reply from DaemonMessage type}
    Y -- Get --> Z["Call match_get_commands()"]
    Y -- Set --> AA["Call match_set_commands()"]
    Y -- Listen --> AB[Add client to clients list]

    Z --> AC[Send reply to sender]
    AA --> AC
    AC --> U

    U -- Shutdown Event --> W
  end

  T --> S
  T --> U

%% ---------- Spawn Poller ----------
  subgraph SPAWN_POLLER ["spawn_poller::<P>()"]
    AI{Timer Ticked or Shutdown}

    AI -- Timer Tick --> AJ["Call P::poll()"]
    AJ --> AK["Call update_snapshot(new_value)"]
    AK --> AI

    AI -- Shutdown Event --> AL["Close spawn_poller::<P>()"]
  end

  R --> AI

Loading

Requirements

• wpctl (Pipewire) for volume control
• brightnessctl for keyboard and monitor brightness control (Devices are set manually in the code)
• bluetoothctl for bluetooth control
• free for viewing memory usage
• acpi for viewing battery stats
• asusctl for fan-speed control