ac: add page (#9053)

pages/common/ac.md

@@ -0,0 +1,20 @@
+# ac
+
+> Print statistics on how long users have been connected.
+> More information: <https://man.openbsd.org/ac>.
+
+- Print how long the current user has been connected in hours:
+
+`ac`
+
+- Print how long users have been connected in hours:
+
+`ac -p`
+
+- Print how long a particular user has been connected in hours:
+
+`ac -p {{username}}`
+
+- Print how long a particular user has been connected in hours per day (with total):
+
+`ac -dp {{username}}`