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NetBSD 6.1.5 - man page for vsyslog (netbsd section 3)

SYSLOG(3)			   BSD Library Functions Manual 			SYSLOG(3)

     syslog, syslog_r, vsyslog, vsyslog_r, syslogp, syslogp_r, vsyslogp, vsyslogp_r, openlog,
     openlog_r, closelog, closelog_r, setlogmask, setlogmask_r -- control system log

     Standard C Library (libc, -lc)

     #include <syslog.h>

     syslog(int priority, const char *message, ...);

     syslog_r(int priority, struct syslog_data *data, const char *message, ...);

     syslogp(int priority, const char *msgid, const char *sdfmt, const char *message, ...);

     syslogp_r(int priority, struct syslog_data *data, const char *msgid, const char *sdfmt,
	 const char *message, ...);

     openlog(const char *ident, int logopt, int facility);

     openlog_r(const char *ident, int logopt, int facility, struct syslog_data *data);


     closelog_r(struct syslog_data *data);

     setlogmask(int maskpri);

     setlogmask_r(int maskpri, struct syslog_data *data);

     #include <stdarg.h>

     vsyslog(int priority, const char *message, va_list args);

     vsyslog_r(int priority, struct syslog_data *data, const char *message, va_list args);

     vsyslogp(int priority, const char *msgid, const char *sdfmt, const char *message,
	 va_list args);

     vsyslogp_r(int priority, struct syslog_data *data, const char *msgid, const char *sdfmt,
	 const char *message, va_list args);

     The syslog() function writes message to the system message logger.  The message is then
     written to the system console, log files, logged-in users, or forwarded to other machines as
     appropriate (see syslogd(8)).

     The message is identical to a printf(3) format string, except that '%m' is replaced by the
     current error message.  (As denoted by the global variable errno; see strerror(3).)  A
     trailing newline is added if none is present.

     The syslog_r() function is a multithread-safe version of the syslog() function.  It takes a
     pointer to a syslog_data structure which is used to store information.  This parameter must
     be initialized before syslog_r() is called.  The SYSLOG_DATA_INIT constant is used for this
     purpose.  The syslog_data structure and the SYSLOG_DATA_INIT constant are defined as:

	   struct syslog_data {
		   int		   log_file;
		   int		   connected;
		   int		   opened;
		   int		   log_stat;
		   const char	  *log_tag;
		   int		   log_fac;
		   int		   log_mask;

	   #define SYSLOG_DATA_INIT { \
	       .log_file = -1, \
	       .log_fac = LOG_USER, \
	       .log_mask = 0xff, \

     The structure is composed of the following elements:

	   log_file   contains the file descriptor of the file where the message is logged

	   connected  indicates if connect has been done

	   opened     indicates if openlog_r() has been called

	   log_stat   status bits, set by openlog_r()

	   log_tag    string to tag the entry with

	   log_fac    facility code

	   log_mask   mask of priorities to be logged

     The vsyslog() function is an alternative form in which the arguments have already been cap-
     tured using the variable-length argument facilities of stdarg(3).

     The syslogp() variants take additional arguments which correspond to new fields in the sys-
     log-protocol message format.  All three arguments are evaluated as printf(3) format strings
     and any of them can be NULL.  This enables applications to use message IDs, structured data,
     and UTF-8 encoded content in messages.

     The message is tagged with priority.  Priorities are encoded as a facility and a level.  The
     facility describes the part of the system generating the message.	The level is selected
     from the following ordered (high to low) list:

     LOG_EMERG	   A panic condition.  This is normally broadcast to all users.

     LOG_ALERT	   A condition that should be corrected immediately, such as a corrupted system

     LOG_CRIT	   Critical conditions, e.g., hard device errors.

     LOG_ERR	   Errors.

     LOG_WARNING   Warning messages.

     LOG_NOTICE    Conditions that are not error conditions, but should possibly be handled spe-

     LOG_INFO	   Informational messages.

     LOG_DEBUG	   Messages that contain information normally of use only when debugging a pro-

     The vsyslog_r() is used the same way as vsyslog() except that it takes an additional pointer
     to a syslog_data structure.  It is a multithread-safe version of the vsyslog() function
     described above.

     The openlog() function provides for more specialized processing of the messages sent by
     syslog() and vsyslog().  The parameter ident is a string that will be prepended to every
     message.  The logopt argument is a bit field specifying logging options, which is formed by
     OR'ing one or more of the following values:

     LOG_CONS	   If syslog() cannot pass the message to syslogd(8) it will attempt to write the
		   message to the console (``/dev/console'').

     LOG_NDELAY    Open the connection to syslogd(8) immediately.  Normally the open is delayed
		   until the first message is logged.  Useful for programs that need to manage
		   the order in which file descriptors are allocated.

     LOG_PERROR    Write the message to standard error output as well to the system log.

     LOG_PID	   Log the process id with each message: useful for identifying instantiations of
		   daemons.  (This PID is placed within brackets between the ident and the mes-

     The facility parameter encodes a default facility to be assigned to all messages that do not
     have an explicit facility encoded:

     LOG_AUTH	   The authorization system: login(1), su(1), getty(8), etc.

     LOG_AUTHPRIV  The same as LOG_AUTH, but logged to a file readable only by selected individu-

     LOG_CRON	   The cron daemon: cron(8).

     LOG_DAEMON    System daemons, such as routed(8), that are not provided for explicitly by
		   other facilities.

     LOG_FTP	   The file transfer protocol daemon: ftpd(8).

     LOG_KERN	   Messages generated by the kernel.  These cannot be generated by any user pro-

     LOG_LPR	   The line printer spooling system: lpr(1), lpc(8), lpd(8), etc.

     LOG_MAIL	   The mail system.

     LOG_NEWS	   The network news system.

     LOG_SYSLOG    Messages generated internally by syslogd(8).

     LOG_USER	   Messages generated by random user processes.  This is the default facility
		   identifier if none is specified.

     LOG_UUCP	   The uucp system.

     LOG_LOCAL0    Reserved for local use.  Similarly for LOG_LOCAL1 through LOG_LOCAL7.

     The openlog_r() function is the multithread-safe version of the openlog() function.  It
     takes an additional pointer to a syslog_data structure.  This function must be used in con-
     junction with the other multithread-safe functions.

     The closelog() function can be used to close the log file.

     The closelog_r() does the same thing as closelog(3) but in a multithread-safe way and takes
     an additional pointer to a syslog_data structure.

     The setlogmask() function sets the log priority mask to maskpri and returns the previous
     mask.  Calls to syslog() with a priority not set in maskpri are rejected.	The mask for an
     individual priority pri is calculated by the macro LOG_MASK(pri); the mask for all priori-
     ties up to and including toppri is given by the macro LOG_UPTO(toppri).  The default allows
     all priorities to be logged.

     The setlogmask_r() function is the multithread-safe version of setlogmask().  It takes an
     additional pointer to a syslog_data structure.

     The routines closelog(), closelog_r(), openlog(), openlog_r(), syslog(), syslog_r(),
     vsyslog(), vsyslog_r(), syslogp(), syslogp_r(), vsyslogp(), and vsyslogp_r() return no

     The routines setlogmask() and setlogmask_r() always return the previous log mask level.

	   syslog(LOG_ALERT, "who: internal error 23");

	   openlog("ftpd", LOG_PID | LOG_NDELAY, LOG_FTP);


	   syslog(LOG_INFO, "Connection from host %d", CallingHost);

	   syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");

	   syslogp(LOG_INFO|LOG_LOCAL2, NULL, NULL, "foobar error: %m");

	   syslogp(LOG_INFO, "ID%d", "[meta language=\"en-US\"]",
		   "event: %s", 42, EventDescription);

     For the multithread-safe functions:

	   struct syslog_data sdata = SYSLOG_DATA_INIT;

	   syslog_r(LOG_INFO|LOG_LOCAL2, &sdata, "foobar error: %m");

     logger(1), syslogd(8)

     The BSD syslog Protocol, RFC, 3164, August 2001.

     The syslog Protocol, Internet-Draft, draft-ietf-syslog-protocol-23, September 2007.

     These non-multithread-safe functions appeared in 4.2BSD.  The multithread-safe functions
     appeared in OpenBSD 3.1 and then in NetBSD 4.0.  The async-signal-safe functions appeared in
     NetBSD 4.0.  The syslog-protocol functions appeared in NetBSD 5.0.

     It is important never to pass a string with user-supplied data as a format without using
     '%s'.  An attacker can put format specifiers in the string to mangle your stack, leading to
     a possible security hole.	This holds true even if you have built the string ``by hand''
     using a function like snprintf(), as the resulting string may still contain user-supplied
     conversion specifiers for later interpolation by syslog().

     Always be sure to use the proper secure idiom:

	   syslog(priority, "%s", string);

     With syslogp() the caller is responsible to use the right formatting for the message fields.
     A msgid must only contain up to 32 ASCII characters.  A sdfmt has strict rules for paranthe-
     sis and character quoting.  If the msgfmt contains UTF-8 characters, then it has to start
     with a Byte Order Mark.

BSD					   May 3, 2010					      BSD

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