SYSLOG(3)						     Linux Programmer's Manual							 SYSLOG(3)

NAME

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

SYNOPSIS

       #include <syslog.h>

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

       #include <stdarg.h>

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

DESCRIPTION

       closelog() closes the descriptor being used to write to the system logger.  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 typ-
       ically 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 syslogd(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 is added when needed.

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

PARAMETERS

       This section lists 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
	      Don't 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 SUSv3.) 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 logging 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

       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 1003.1-2001.  POSIX 1003.1-2001
       specifies only the LOG_USER and LOG_LOCAL* values for facility.	However, with the exception of LOG_AUTHPRIV and LOG_FTP, the other  facil-
       ity  values  appear  on most Unix systems.  The LOG_PERROR value for option is not specified by POSIX 1003.1-2001, but is available in most
       versions of Unix.

HISTORY

       A syslog function call appeared in BSD 4.2.  BSD 4.3 documents openlog(), syslog(), closelog(), and setlogmask().  4.3BSD-Reno  also  docu-
       ments vsyslog().  Of course early v* functions used the <varargs.h> mechanism, which is not compatible with <stdarg.h>.

NOTES

       The  parameter  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
	      syslog("%s", string);
       instead.

SEE ALSO

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

Linux								    2002-01-03								 SYSLOG(3)