Make clear that it is a Nagios plugin and cleaner code

monitoring/check_valisechaprilorg_update

@@ -22,11 +22,22 @@
 # This checks for updates of nextcloud components.
 # If any update is present, they are listed in human readable form on stdout, and 1 is returned,
 # and if everything is OK, tell it on stdout "OK", and returns 0.
+#
+# This is a Nagios plugin and thus follows its return code standards
 # ================================================
 
+
+
 # Configuration data
 NEXTCLOUD_ROOT="/var/www/valise.chapril.org"
 
+# Constants for return codes
+readonly NS_OK=0
+readonly NS_WARNING=1
+readonly NS_CRITICAL=1
+readonly NS_UNKNOWN=1
+
+
 # Returns script usage
 function usage() 
 {
@@ -36,7 +47,7 @@ function usage()
 # Main entry point
 
 # By default, we assume to fail
-EXIT_RESULT=1
+EXIT_RESULT=${NS_UNKNOWN}
 
 # Usage check
 if [ "$#" -ne 0 ]
@@ -51,6 +62,7 @@ else
 
 	if [ $? != 0 ]
 	then
+		EXIT_RESULT=${NS_CRITICAL}
         	echo "Failed to check Nextcloud update"
 	else
 
@@ -59,9 +71,10 @@ else
 
 		if [ $? == 0 ]
 		then 
+			EXIT_RESULT=${NS_OK}
 			echo "OK"
-			EXIT_RESULT=0
 		else
+			EXIT_RESULT=${NS_WARNING}
 			echo ${UPDATE_LIST}
 		fi