SYSLOG(3)		   Linux Programmers Manual		    SYSLOG(3)



NAME
       closelog, openlog, syslog, vsyslog - send messages to the system logger

SYNOPSIS
       #include 

       void openlog(const char *ident, int option, int facility);
       void syslog(int priority, const char *format, ...);
       void closelog(void);

       #include 

       void vsyslog(int priority, const char *format, va_list ap);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       vsyslog(): _BSD_SOURCE

DESCRIPTION
       closelog() closes the descriptor being used to write to the system log
       ger.  The use of closelog() is optional.

       openlog()  opens  a connection to the system logger for a program.  The
       string pointed to by ident is prepended to every message, and is  typi
       cally  set  to  the  program name.  The option argument specifies flags
       which control the operation of openlog() and subsequent calls  to  sys
       log().	The facility argument establishes a default to be used if none
       is specified in subsequent calls to syslog().  Values  for  option  and
       facility  are  given  below.  The use of openlog() is optional; it will
       automatically be called by syslog() if necessary, in which  case  ident
       will default to NULL.

       syslog()  generates  a  log  message, which will be distributed by sys
       logd(8).  The priority argument is formed by ORing the facility and the
       level  values (explained below).  The remaining arguments are a format,
       as in printf(3) and any arguments required by the format,  except  that
       the  two  character  sequence  %m will be replaced by the error message
       string strerror(errno).	A trailing newline may be added if needed.

       The function vsyslog() performs the same task as syslog() with the dif
       ference that it takes a set of arguments which have been obtained using
       the stdarg(3) variable argument list macros.

       The subsections below list the parameters used to  set  the  values  of
       option, facility, and priority.

   option
       The option argument to openlog() is an OR of any of these:

       LOG_CONS
	      Write  directly  to  system  console  if there is an error while
	      sending to system logger.

       LOG_NDELAY
	      Open the connection immediately  (normally,  the	connection  is
	      opened when the first message is logged).

       LOG_NOWAIT
	      Dont  wait for child processes that may have been created while
	      logging the message.  (The GNU C library does not create a child
	      process, so this option has no effect on Linux.)

       LOG_ODELAY
	      The converse of LOG_NDELAY; opening of the connection is delayed
	      until syslog() is called.  (This is the default, and need not be
	      specified.)

       LOG_PERROR
	      (Not in POSIX.1-2001.)  Print to stderr as well.

       LOG_PID
	      Include PID with each message.

   facility
       The  facility  argument is used to specify what type of program is log
       ging the message.  This lets the configuration file specify  that  mes
       sages from different facilities will be handled differently.

       LOG_AUTH
	      security/authorization  messages	(DEPRECATED  Use  LOG_AUTHPRIV
	      instead)

       LOG_AUTHPRIV
	      security/authorization messages (private)

       LOG_CRON
	      clock daemon (cron and at)

       LOG_DAEMON
	      system daemons without separate facility value

       LOG_FTP
	      ftp daemon

       LOG_KERN
	      kernel messages

       LOG_LOCAL0 through LOG_LOCAL7
	      reserved for local use

       LOG_LPR
	      line printer subsystem

       LOG_MAIL
	      mail subsystem

       LOG_NEWS
	      USENET news subsystem

       LOG_SYSLOG
	      messages generated internally by syslogd(8)

       LOG_USER (default)
	      generic user-level messages

       LOG_UUCP
	      UUCP subsystem

   level
       This determines the importance of the  message.	 The  levels  are,  in
       order of decreasing importance:

       LOG_EMERG
	      system is unusable

       LOG_ALERT
	      action must be taken immediately

       LOG_CRIT
	      critical conditions

       LOG_ERR
	      error conditions

       LOG_WARNING
	      warning conditions

       LOG_NOTICE
	      normal, but significant, condition

       LOG_INFO
	      informational message

       LOG_DEBUG
	      debug-level message

       The function setlogmask(3) can be used to restrict logging to specified
       levels only.

CONFORMING TO
       The functions openlog(), closelog(), and syslog() (but  not  vsyslog())
       are  specified  in SUSv2 and POSIX.1-2001.  POSIX.1-2001 specifies only
       the LOG_USER and LOG_LOCAL* values for  facility.   However,  with  the
       exception of LOG_AUTHPRIV and LOG_FTP, the other facility values appear
       on most Unix systems.  The LOG_PERROR value for option is not specified
       by POSIX.1-2001, but is available in most versions of Unix.

NOTES
       The  argument  ident in the call of openlog() is probably stored as-is.
       Thus, if the string  it	points	to  is	changed,  syslog()  may  start
       prepending the changed string, and if the string it points to ceases to
       exist, the results are undefined.  Most portable is  to	use  a	string
       constant.

       Never  pass  a string with user-supplied data as a format, use the fol
       lowing instead:

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

SEE ALSO
       logger(1), setlogmask(3), syslog.conf(5), syslogd(8)

COLOPHON
       This page is part of release 3.05 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



Linux				  2007-07-26			     SYSLOG(3)