-.B \-ping\-source list | file | subnet
-Th source of the list of hosts to ping. Valid values are: \fIlist\fP,
-\fIfile\fP, \fIsubnet\fP. The first two values are described below;
-and \fIsubnet\fP indicates that the sonar should ping all hosts in the
-same subnet as the current machine. (All addresses are treated
-as class C nets, therefore this will at most ping 254 hosts.)
-.TP 8
-.B \-ping\-file \fIfilename\fP
-The path to a file listing the hosts to ping. This file can be in the
+.B \-ping \fIhosts-or-subnets\fP
+The list of things to ping, separated by commas or spaces.
+Elements of this list may be:
+.RS 8
+.TP 12
+.B simulation
+to run in simulation mode, instead of pinging real hosts (this is the default
+if the program is not installed setuid);
+.TP 12
+.I hostname
+to ping the given host;
+.TP 12
+.I A.B.C.D
+to ping the given IP address;
+.TP 12
+.B subnet
+to ping the local class C subnet (the nearest 255 addresses);
+.TP 12
+.B subnet/\fINN\fP
+to ping a different-sized local subnet: e.g., \fBsubnet/28\fP would ping
+a 4-bit subnet (the nearest 15 addresses);
+.TP 12
+.I A.B.C.D/NN
+to ping an arbitrary other subnet: the IP address specifies the base address,
+and the part after the slash is how wide the subnet is. Typical values
+are /24 (for 255 addresses) and /28 (for 15 addresses.)
+.TP 12
+.I filename
+to ping the hosts listed in the given file. This file can be in the