Notify logged-in users when updates are availble.

2 files changed, 21 insertions, 0 deletions

diff --git a/README.md b/README.md
index 626f28c..92a6e95 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,11 @@ updates for packages which have bugs (or remove already-downloaded updates).
 
 So, look into a way of doing that.
 
+### Notifying users about updates
+
+Find a better way of getting a list of logged in users and their DBus session
+bus address than `find /run/user -type s -name bus`.
+
 
 ## License
 
diff --git a/adu-download b/adu-download
index 7c9a08c..574eeae 100755
--- a/adu-download
+++ b/adu-download
@@ -35,4 +35,20 @@ fi
 apt-get -q -y --with-new-pkgs --download-only upgrade | grep "^Get:"
 
 ln -s -- "${UPDATE_TARGET}" "${UPDATE_SYMLINK}" 2>/dev/null || true
+
+# Notify logged-in users that updates are available
+if command -v notify-send >/dev/null; then
+	# Disable shellcheck's "For loops over find output are fragile" warning here
+	# because filenames in `/run/user` are safe, and doing it The Right Way is a
+	# pain because of the environment variable.
+	# shellcheck disable=SC2044
+	for addr in $(find /run/user -type s -name bus 2>/dev/null); do
+		export DBUS_SESSION_BUS_ADDRESS="unix:path=$addr";
+		runuser -u "$(stat -c "%U" "$addr")" -- \
+			notify-send --app-name=apt-desktop-upgrades \
+			"$upgrades system updates available" \
+			"Reboot when it is convenient to install them"
+	done
+fi
+
 echo "$upgrades updates available"