Homebrew/homebrew-cask · warning

Unable to forcibly close TeamViewer

Error message

Unable to forcibly close TeamViewer

What it means

Printed by the terminate_process step inside teamviewer's postflight_steps (Casks/t/teamviewer.rb:76). TeamViewer's .pkg postinstall launches the app, so Homebrew runs `/usr/bin/pkill -f /Applications/TeamViewer.app` up to 3 times, 1 second apart. pkill returns non-zero when no process's full command line matches that path or when signalling is not permitted; after the last failed attempt the failure_message is printed as a `Warning:` via opoo. With `must_succeed: false` the step is non-fatal — the warning only indicates the pattern never matched, not that the cask install failed.

Source

Thrown at Casks/t/teamviewer.rb:76

  desc "Remote access and connectivity software focused on security"
  homepage "https://www.teamviewer.com/"

  auto_updates true
  conflicts_with cask: "teamviewer-host"
  depends_on :macos

  postflight_steps do
    # postinstall launches the app
    terminate_process(
      "/Applications/TeamViewer.app",
      match:           :full,
      attempts:        3,
      must_succeed:    false,
      notices:         [
        "The TeamViewer package postinstall script launches the TeamViewer app",
        "Attempting to close the TeamViewer app to avoid unwanted user intervention",
      ],
      failure_message: "Unable to forcibly close TeamViewer",
    )
  end

  uninstall launchctl: [
              "com.teamviewer.desktop",
              "com.teamviewer.Helper",
              "com.teamviewer.service",
              "com.teamviewer.teamviewer",
              "com.teamviewer.teamviewer_desktop",
              "com.teamviewer.teamviewer_service",
              "com.teamviewer.UninstallerHelper",
              "com.teamviewer.UninstallerWatcher",
            ],
            quit:      [
              "com.teamviewer.TeamViewer",
              "com.teamviewer.TeamViewerUninstaller",
            ],
            pkgutil:   [

View on GitHub (pinned to 8587086220)

Solutions

  1. If brew completed, treat the warning as advisory (`must_succeed: false`); quit any leftover app with `pkill -f /Applications/TeamViewer.app`.
  2. Quit TeamViewer from its menu-bar icon or `osascript -e 'quit app "TeamViewer"'` before the brew operation, then re-run.
  3. If TeamViewer keeps coming back, stop the respawning service first: `sudo launchctl bootout system/com.teamviewer.service` (also check com.teamviewer.teamviewer_service), then `brew reinstall --cask teamviewer`.
  4. Verify with `pgrep -fl TeamViewer` which instance (and path) is actually alive; if it differs from /Applications/TeamViewer.app, the cask path is stale — `brew edit --cask teamviewer` and open a PR.
  5. Disable 'Start TeamViewer with system' in TeamViewer preferences before upgrades to avoid respawn races.

Example fix

# before
brew upgrade --cask teamviewer
# Warning: Unable to forcibly close TeamViewer

# after: quit the app and stop the root service, then upgrade
osascript -e 'quit app "TeamViewer"'
sudo launchctl bootout system/com.teamviewer.service 2>/dev/null || true
brew upgrade --cask teamviewer
Defensive patterns

Strategy: validation

Validate before calling

# Quit the app AND stop the root service that can relaunch it:
osascript -e 'quit app "TeamViewer"' 2>/dev/null || true
sudo launchctl bootout system/com.teamviewer.service 2>/dev/null || true
brew reinstall --cask teamviewer

Try / catch

begin
  Homebrew::SystemCommand.run!("/usr/bin/pkill", args: ["-f", "/Applications/TeamViewer.app"])
rescue ErrorDuringExecution
  # Nothing matched, or a root-owned service respawned beyond reach.
  warn "Unable to forcibly close TeamViewer"
end

Prevention

When it happens

Trigger: `brew install|upgrade|reinstall --cask teamviewer` where each pkill attempt finds nothing to signal: postinstall's launch never happened (headless Mac, no GUI login), the app appeared after the ~3s window, a running TeamViewer executes from a different path, or a root-owned/respawned instance (TeamViewer runs com.teamviewer.service and several launchd jobs listed in the uninstall stanza) could not be signalled by the user-level pkill.

Common situations: MacOS boxes where TeamViewer is configured as a system service ('start with system') so the app is spawned by a root daemon rather than the pkg postinstall; SSH/CI installs; user quits the app during the retry window; vendor renames TeamViewer.app in a pkg update.

Related errors

AI-assisted analysis of Homebrew/homebrew-cask@8587086220 (2026-08-21). Data as JSON: /api/errors/4261e5e0b50403ba. Report an issue: GitHub.