Update homebrew periodically on macOS - place in ~/Library/LaunchAgents/

brew-update.plist

<?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">

<!-- `brew update` every 6 hours -->

<plist version="1.0">
<dict>
  <key>EnableGlobbing</key>
  <false/>

  <key>Label</key>
  <string>io.scw.brew-update</string>

  <key>ProgramArguments</key>
  <array>
    <string>/usr/local/bin/brew</string>
    <string>update</string>
  </array>

  <key>StartInterval</key>
  <integer>21600</integer>

  <key>RunAtLoad</key>
  <true/>

  <key>StandardErrorPath</key>
  <string>/tmp/io.scw.brew-update.err</string>

  <key>StandardOutPath</key>
  <string>/tmp/io.scw.brew-update.out</string>

</dict>
</plist>