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log(7D)				    Devices			       log(7D)

NAME
       log - interface to STREAMS error	logging	and event tracing

SYNOPSIS
       #include	<sys/strlog.h>

       #include	<sys/log.h>

DESCRIPTION
       log  is a STREAMS software device driver	that provides an interface for
       console logging and for the STREAMS error  logging  and	event  tracing
       processes  (see	strerr(1M), and	strace(1M)). log presents two separate
       interfaces: a function call  interface  in  the	kernel	through	 which
       STREAMS drivers and modules submit log messages;	and a set of  ioctl(2)
       requests	and STREAMS messages for interaction with a user level console
       logger, an error	logger,	a trace	logger,	or processes that need to sub-
       mit their own log messages.

   Kernel Interface
       log messages are	generated within the kernel by calls to	 the  function
       strlog():

       strlog(short mid,
	   short sid,
	   char	level,
	   ushort_t flags,
	   char	*fmt,
	   unsigned arg1...
       );

       Required	 definitions are contained in <sys/strlog.h>, <sys/log.h>, and
       <sys/syslog.h>. mid is the STREAMS module id number for the  module  or
       driver  submitting  the	log  message. sid is an	internal sub-id	number
       usually used to identify	a particular minor  device of a	driver.	 level
       is a tracing level that allows for selective screening out of low  pri-
       ority messages from the tracer. flags are any combination of   SL_ERROR
       (the  message  is  for the error	logger),  SL_TRACE (the	message	is for
       the tracer), SL_CONSOLE (the message is for the console logger),	SL_FA-
       TAL  (advisory  notification of a fatal error), and  SL_NOTIFY (request
       that a copy of the message be mailed to the system administrator).  fmt
       is  a  printf(3C) style format string, except that  %s, %e, %E, %g, and
       %G conversion specifications are	not handled. Up	to  NLOGARGS (in  this
       release,	three) numeric or character arguments can be provided.

   User	Interface
       log  is implemented as a	cloneable device, it clones itself without in-
       tervention from the system clone	device.	Each open of /dev/log  obtains
       a  separate  stream to log. In order to receive log messages, a process
       must first notify log whether it	is an error logger, trace  logger,  or
       console	logger	using a	STREAMS	 I_STR ioctl call (see below). For the
       console logger, the  I_STR ioctl	has an	ic_cmd	field  of   I_CONSLOG,
       with  no	 accompanying data. For	the error logger, the  I_STR ioctl has
       an  ic_cmd field	of  I_ERRLOG, with no accompanying data. For the trace
       logger,	the   ioctl has	an  ic_cmd field of  I_TRCLOG, and must	be ac-
       companied by a data buffer containing an	array of one  or  more	struct
       trace_ids elements.

       struct trace_ids	{
	   short ti_mid;
	   short ti_sid;
	   char	 ti_level;
       };

       Each  trace_ids	structure  specifies a mid, sid, and level  from which
       messages	will be	accepted. strlog(9F) will accept  messages  whose  mid
       and sid exactly match those in the trace_ids structure, and whose level
       is less than or equal to	the level given	in the trace_ids structure.  A
       value  of  -1 in	any of the fields of the trace_ids structure indicates
       that  any value is accepted for that field.

       Once the	logger process has identified itself using the ioctl call, log
       will begin sending up messages subject to the restrictions noted	above.
       These messages are obtained using the  getmsg(2)	function. The  control
       part  of	this message contains a	log_ctl	structure, which specifies the
       mid, sid, level,	flags, time in	ticks since boot that the message  was
       submitted,  the corresponding time in seconds since Jan.	1, 1970, a se-
       quence number, and a priority. The time in seconds since	1970  is  pro-
       vided  so that the date and time	of the message can be easily computed,
       and the time in ticks since boot	is provided so that the	relative  tim-
       ing of log messages can be determined.

       struct log_ctl {
	   short mid;
	   short sid;
	   char	 level;	    /* level of	message	for tracing */
	   short flags;	    /* message disposition */
       #if defined(_LP64)  ||  defined(_I32LPx)
	   clock32_t ltime; /* time in machine ticks since boot	*/
	   time32_t ttime;  /* time in seconds since 1970 */
       #else
	   clock_t ltime;
	   time_t  ttime;
       #endif
	   int	seq_no;	    /* sequence	number */
	   int	pri;	    /* priority	= (facility|level) */
       };

       The  priority consists of a priority code and a facility	code, found in
       <sys/syslog.h>. If SL_CONSOLE is	set in flags, the priority code	is set
       as follows: If SL_WARN is set, the priority code	is set to LOG_WARNING;
       If SL_FATAL is set, the priority	code is	set to LOG_CRIT; If   SL_ERROR
       is  set,	 the priority code is set to  LOG_ERR; If  SL_NOTE is set, the
       priority	code is	set to	LOG_NOTICE; If	SL_TRACE is set, the  priority
       code  is	 set  to   LOG_DEBUG; If only  SL_CONSOLE is set, the priority
       code is set to  LOG_INFO. Messages originating from the kernel have the
       facility	code set to LOG_KERN. Most messages originating	from user pro-
       cesses will have	the facility code set to LOG_USER.

       Different sequence numbers are maintained for the error and trace  log-
       ging streams, and are provided so that gaps in the sequence of messages
       can be determined (during times of high message traffic	some  messages
       may  not	be delivered by	the logger to avoid hogging system resources).
       The data	part of	the message contains the unexpanded text of the	format
       string (null terminated), followed by  NLOGARGS words for the arguments
       to the format string, aligned on	the first word boundary	following  the
       format string.

       A process may also send a message of the	same structure to log, even if
       it is not an error or trace logger. The	only  fields  of  the  log_ctl
       structure  in the control part of the message that are accepted are the
       level, flags, and pri fields; all other fields are filled in by log be-
       fore  being  forwarded to the appropriate logger. The data portion must
       contain a null terminated format	string,	and any	arguments (up to NLOG-
       ARGS)  must  be packed, 32-bits each,  on the next 32-bit boundary fol-
       lowing the end of the format string.

       ENXIO is	returned for  I_TRCLOG ioctls  without	any  trace_ids	struc-
       tures, or for any unrecognized ioctl calls. The driver silently ignores
       incorrectly formatted log messages sent to the driver by	a user process
       (no error results).

       Processes that wish to write a message to the console logger may	direct
       their output to /dev/conslog, using either write(2) or putmsg(2).

   Driver Configuration
       The following driver configuration properties may  be  defined  in  the
       log.conf	file.

       msgid=1	       If  msgid=1, each message will be preceded by a message
		       ID as described in syslogd(1M).

       msgid=0		If msgid=0, message IDs	will not  be  generated.  This
		       property	is unstable and	may be removed in a future re-
		       lease.

EXAMPLES
       Example 1: I_ERRLOG registration.

       struct strioctl ioc;
       ioc.ic_cmd = I_ERRLOG;
       ioc.ic_timout = 0;	/* default timeout (15 secs.) */
       ioc.ic_len = 0;
       ioc.ic_dp = NULL;
       ioctl(log, I_STR, &ioc);

       Example 2: I_TRCLOG registration.

       struct trace_ids	tid[2];
       tid[0].ti_mid = 2;
       tid[0].ti_sid = 0;
       tid[0].ti_level = 1;
       tid[1].ti_mid = 1002;
       tid[1].ti_sid = -1;		 /* any	sub-id will be allowed */
       tid[1].ti_level = -1;		 /* any	level will be allowed */
       ioc.ic_cmd = I_TRCLOG;
       ioc.ic_timout = 0;
       ioc.ic_len = 2 *	sizeof(struct trace_ids);
       ioc.ic_dp = (char *)tid;
       ioctl(log, I_STR, &ioc);

       Example of submitting a log message (no arguments):

       struct strbuf ctl, dat;
       struct log_ctl lc;
       char *message = "Don't forget to	pick up	some milk
			on the way home";
       ctl.len = ctl.maxlen = sizeof(lc);
       ctl.buf = (char *)&lc;
       dat.len = dat.maxlen = strlen(message);
       dat.buf = message;
       lc.level	= 0;
       lc.flags	= SL_ERROR|SL_NOTIFY;
       putmsg(log, &ctl, &dat, 0);

FILES
       /dev/log		       Log driver.

       /dev/conslog	       Write only instance of the log driver, for con-
			       sole logging.

       /kernel/drv/log.conf    Log configuration file.

SEE ALSO
       strace(1M),   strerr(1M),  intro(3),  getmsg(2),	 ioctl(2),  putmsg(2),
       write(2), printf(3C), strlog(9F)

       STREAMS Programming Guide

SunOS 5.10			  11 Mar 1998			       log(7D)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | FILES | SEE ALSO

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