4.4BSD/usr/share/man/cat8/rwhod.0

RWHOD(8)                  BSD System Manager's Manual                 RWHOD(8)

NNAAMMEE
     rrwwhhoodd - system status server

SSYYNNOOPPSSIISS
     rrwwhhoodd

DDEESSCCRRIIPPTTIIOONN
     RRwwhhoodd is the server which maintains the database used by the rwho(1) and
     ruptime(1) programs.  Its operation is predicated on the ability to
     _b_r_o_a_d_c_a_s_t messages on a network.

     RRwwhhoodd operates as both a producer and consumer of status information.  As
     a producer of information it periodically queries the state of the system
     and constructs status messages which are broadcast on a network.  As a
     consumer of information, it listens for other rrwwhhoodd servers' status mes-
     sages, validating them, then recording them in a collection of files lo-
     cated in the directory _/_v_a_r_/_r_w_h_o.

     The server transmits and receives messages at the port indicated in the
     ``rwho'' service specification; see services(5).  The messages sent and
     received, are of the form:

           struct  outmp {
                   char    out_line[8];            /* tty name */
                   char    out_name[8];            /* user id */
                   long    out_time;               /* time on */
           };

           struct  whod {
                   char    wd_vers;
                   char    wd_type;
                   char    wd_fill[2];
                   int     wd_sendtime;
                   int     wd_recvtime;
                   char    wd_hostname[32];
                   int     wd_loadav[3];
                   int     wd_boottime;
                   struct  whoent {
                           struct  outmp we_utmp;
                           int     we_idle;
                   } wd_we[1024 / sizeof (struct whoent)];
           };

     All fields are converted to network byte order prior to transmission.
     The load averages are as calculated by the w(1) program, and represent
     load averages over the 5, 10, and 15 minute intervals prior to a server's
     transmission; they are multiplied by 100 for representation in an inte-
     ger.  The host name included is that returned by the gethostname(2) sys-
     tem call, with any trailing domain name omitted.  The array at the end of
     the message contains information about the users logged in to the sending
     machine.  This information includes the contents of the utmp(5) entry for
     each non-idle terminal line and a value indicating the time in seconds
     since a character was last received on the terminal line.

     Messages received by the rwho server are discarded unless they originated
     at an rwho server's port.  In addition, if the host's name, as specified
     in the message, contains any unprintable ASCII characters, the message is
     discarded.  Valid messages received by rrwwhhoodd are placed in files named
     _w_h_o_d_._h_o_s_t_n_a_m_e in the directory _/_v_a_r_/_r_w_h_o. These files contain only the
     most recent message, in the format described above.

     Status messages are generated approximately once every 3 minutes.  RRwwhhoodd
     performs an nlist(3) on _/_v_m_u_n_i_x every 30 minutes to guard against the
     possibility that this file is not the system image currently operating.

SSEEEE AALLSSOO
     rwho(1),  ruptime(1)

BBUUGGSS
     There should be a way to relay status information between networks.  Sta-
     tus information should be sent only upon request rather than continuous-
     ly.  People often interpret the server dying or network communtication
     failures as a machine going down.

HHIISSTTOORRYY
     The rrwwhhoodd command appeared in 4.2BSD.

4.2 Berkeley Distribution        June 6, 1993                                2