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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
       typically set to the program name.  The option argument specifies flags
       which control the operation of openlog() and subsequent calls to
       syslog().  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
       messages 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
       facility 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
       documents 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)

NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | CONFORMING TO | HISTORY | NOTES | SEE ALSO

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