Swift CLI to get or set the sound volume of the main audio device using CoreAudio

swift_volume.swift

// compile with: swiftcc swift_volume.swift -o swiftvol

import CoreAudio
import AudioToolbox
import Foundation

class SystemVolumeManager {
    private let outputDeviceID: AudioDeviceID = AudioObjectID(kAudioObjectSystemObject)

    private func getDefaultOutputDevice() -> AudioDeviceID? {
        var deviceID = AudioDeviceID(0)
        var propertyAddress = AudioObjectPropertyAddress(
            mSelector: kAudioHardwarePropertyDefaultOutputDevice,
            mScope: kAudioObjectPropertyScopeGlobal,
            mElement: kAudioObjectPropertyElementMain
        )
        var deviceIDSize = UInt32(MemoryLayout.size(ofValue: deviceID))
        let status = AudioObjectGetPropertyData(
            outputDeviceID,
            &propertyAddress,
            0,
            nil,
            &deviceIDSize,
            &deviceID
        )
        guard status == noErr else {
            print("Unable to get default output device: \(status)")
            return nil
        }
        return deviceID
    }

    func getVolumeLevel() -> Float? {
        guard let deviceID = getDefaultOutputDevice() else {
            return nil
        }
        var volume: Float = 0
        var propertyAddress = AudioObjectPropertyAddress(
            mSelector: kAudioHardwareServiceDeviceProperty_VirtualMainVolume,
            mScope: kAudioDevicePropertyScopeOutput,
            mElement: kAudioObjectPropertyElementMain
        )
        var size = UInt32(MemoryLayout.size(ofValue: volume))
        let status = AudioObjectGetPropertyData(deviceID, &propertyAddress, 0, nil, &size, &volume)
        guard status == noErr else {
            print("Unable to get volume level: \(status)")
            return nil
        }
        return volume
    }

    func setVolumeLevel(to newVolume: Float) {
        guard let deviceID = getDefaultOutputDevice() else {
            return
        }
        var volume = newVolume
        var propertyAddress = AudioObjectPropertyAddress(
            mSelector: kAudioHardwareServiceDeviceProperty_VirtualMainVolume,
            mScope: kAudioDevicePropertyScopeOutput,
            mElement: kAudioObjectPropertyElementMain
        )
        let status = AudioObjectSetPropertyData(deviceID, &propertyAddress, 0, nil, UInt32(MemoryLayout.size(ofValue: volume)), &volume)
        if status != noErr {
            print("Unable to set volume level: \(status)")
        }
    }
}

// Usage example with CLI arguments
let arguments = CommandLine.arguments
let volumeManager = SystemVolumeManager()

if arguments.count > 1, let newVolume = Float(arguments[1]), newVolume >= 0.0, newVolume <= 1.0 {
    volumeManager.setVolumeLevel(to: newVolume)
    if let updatedVolume = volumeManager.getVolumeLevel() {
        print("Updated volume level: \(updatedVolume)")
    }
} else {
    if let currentVolume = volumeManager.getVolumeLevel() {
        print("Current volume level: \(currentVolume)")
    }
    print("Usage: \(arguments[0]) [volume_level (0.0 - 1.0)]")
}

(after copying swiftvol into a directory in $PATH)

andre@bust ~ % swiftvol .42
Updated volume level: 0.41999996

andre@bust ~ % swiftvol 
Current volume level: 0.41999996
Usage: swiftvol [volume_level (0.0 - 1.0)]