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



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

SYNOPSIS
       #include <&lt;syslog.h>&gt;

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

       #include <&lt;stdarg.h>&gt;

       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
              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 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)