In the context of computing, "agents" are software components that perform automated tasks or services on behalf of users or other programs. These agents are crucial for automating repetitive tasks, monitoring system activities, and managing background processes. While the concept of agents is widely used in various operating systems, macOS has its own mechanisms for handling such tasks, primarily through the use of launch agents and launch daemons.

Launch agents and daemons in macOS are used to run scripts or applications automatically at system startup or at specified intervals. This article will guide you through the process of creating and managing these agents on macOS.

Examples:

1. Creating a Launch Agent: Launch agents are used to run tasks for a specific user. They are stored in the ~/Library/LaunchAgents directory.

   • Step 1: Create a Property List (plist) File Create a .plist file that defines the agent. For example, create a file named com.example.myagent.plist in ~/Library/LaunchAgents/.

     <?xml version="1.0" encoding="UTF-8"?>
     <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
     <plist version="1.0">
     <dict>
      <key>Label</key>
      <string>com.example.myagent</string>
      <key>ProgramArguments</key>
      <array>
          <string>/usr/bin/python3</string>
          <string>/Users/username/scripts/myscript.py</string>
      </array>
      <key>RunAtLoad</key>
      <true/>
      <key>StartInterval</key>
      <integer>3600</integer>
     </dict>
     </plist>

   • Step 2: Load the Launch Agent Use the launchctl command to load the agent.

     launchctl load ~/Library/LaunchAgents/com.example.myagent.plist

   • Step 3: Verify the Agent is Running Check the status of the agent using launchctl.

     launchctl list | grep com.example.myagent

2. Creating a Launch Daemon: Launch daemons run tasks for all users and are stored in /Library/LaunchDaemons.

   • Step 1: Create a Property List (plist) File Create a .plist file named com.example.mydaemon.plist in /Library/LaunchDaemons/.

     <?xml version="1.0" encoding="UTF-8"?>
     <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
     <plist version="1.0">
     <dict>
      <key>Label</key>
      <string>com.example.mydaemon</string>
      <key>ProgramArguments</key>
      <array>
          <string>/usr/bin/python3</string>
          <string>/Users/username/scripts/mydaemon.py</string>
      </array>
      <key>RunAtLoad</key>
      <true/>
      <key>StartInterval</key>
      <integer>7200</integer>
     </dict>
     </plist>

   • Step 2: Load the Launch Daemon Use launchctl with elevated privileges to load the daemon.

     sudo launchctl load /Library/LaunchDaemons/com.example.mydaemon.plist

   • Step 3: Verify the Daemon is Running Check the status of the daemon using launchctl.

     sudo launchctl list | grep com.example.mydaemon