+
+@item runstatedir
+The directory for installing data files which the programs modify
+while they run, that pertain to one specific machine, and which need
+not persist longer than the execution of the program---which is
+generally long-lived, for example, until the next reboot. PID files
+for system daemons are a typical use. In addition, this directory
+should not be cleaned except perhaps at reboot, while the general
+@file{/tmp} (@code{TMPDIR}) may be cleaned arbitrarily. This should
+normally be @file{/var/run}, but write it as
+@file{$(localstatedir)/run}. Having it as a separate variable allows
+the use of @file{/run} if desired, for example. (If you are using
+Autoconf 2.70 or later, write it as @samp{@@runstatedir@@}.)