Introduce example to get pending updates from pacman (#1114)

* Introduce example to get pending updates from pacman

Signed-off-by: Sven Haardiek <sven@haardiek.de>

text_collector_examples/pacman.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+#
+#
+# Description: Expose metrics from pacman updates
+# If installed The bash script *checkupdates*, included with the
+# *pacman-contrib* package, is used to calculate the number of pending updates.
+# Otherwise *pacman* is used for calculation.
+#
+# Author: Sven Haardiek <sven@haardiek.de>
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+if [ -x /usr/bin/checkupdates ]
+then
+    updates=$(/usr/bin/checkupdates | wc -l)
+    cache=0
+else
+    if ! updates=$(/usr/bin/pacman -Qu | wc -l)
+    then
+        updates=0
+    fi
+    cache=1
+fi
+
+echo "# HELP updates_pending number of pending updates from pacman"
+echo "# TYPE updates_pending gauge"
+echo "pacman_updates_pending $updates"
+
+echo "# HELP pacman_updates_pending_from_cache pending updates information are from cache"
+echo "# TYPE pacman_updates_pending_from_cache gauge"
+echo "pacman_updates_pending_from_cache $cache"