STRACE(ADM)                        UNIX System V



     Name
          strace - prints STREAMS trace messages


     Syntax
          strace [ mid sid level ] ...


     Description
          strace without arguments  writes  all  STREAMS  event  trace
          messages  from  all  drivers  and  modules  to  its standard
          output.  These messages are obtained from  the  STREAMS  log
          driver  [log(M)].  If arguments are provided they must be in
          triplets of the form mid, sid, level, where mid is a STREAMS
          module  id  number,  sid  is a sub-id number, and level is a
          tracing priority level.  Each triplet indicates that tracing
          messages  are  to  be received from the given module/driver,
          sub-id (usually indicating minor device), and priority level
          equal to or less than the given level.  The token all may be
          used for any member to  indicate  no  restriction  for  that
          attribute.

          The format of each trace message output is:

          <seq> <time> <ticks> <level> <flags> <mid> <sid> <text>

               <seq>     trace sequence number

               <time>    time of message in hh:mm:ss

               <ticks>   time of message in machine ticks since boot

               <level>   tracing priority level

               <flags>   E : message is also in the error log
                         F : indicates a fatal error
                         N : mail was sent to the system administrator

               <mid>     module id number of source

               <sid>     sub-id number of source

               <text>    formatted text of the trace message

          Once  initiated,  strace  will  continue  to  execute  until
          terminated by the user.


     Examples
          Output all trace messages from the module  or  driver  whose
          module id is 41:

               strace  41 all all

          Output those trace messages from driver/module  id  41  with
          sub-ids 0, 1, or 2:

               strace  41 0 1  41 1 1  41 2 0

          Messages from sub-ids 0 and 1 must have a tracing level less
          than or equal to 1.  Those from sub-id 2 must have a tracing
          level of 0.


     See Also
          log(M), STREAMS Programmer's Guide


     Diagnostics
          Due to performance considerations, only one  strace  process
          is  permitted to open the STREAMS log driver at a time.  The
          log driver has a list  of  the  triplets  specified  in  the
          command   invocation,  and  compares  each  potential  trace
          message  against  this  list  to  decide  if  it  should  be
          formatted  and  sent  up to the strace process.  Hence, long
          lists of triplets will have  a  greater  impact  on  overall
          STREAMS  performance.   Running  strace  will  have the most
          impact on the timing of the modules and  drivers  generating
          the  trace messages that are sent to the strace process.  If
          trace messages are generated faster than the strace  process
          can  handle  them,  then  some of the messages will be lost.
          This last case can be determined by examining  the  sequence
          numbers on the trace messages output.


     (printed 8/23/89)                                  STRACE(ADM)