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NAME

       closelog, openlog, syslog, vsyslog - 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);

   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
       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  may  be  added  if
       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.

       The  subsections  below  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 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
       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(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 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  the
       following instead:

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

SEE ALSO

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

COLOPHON

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       description of the project, and information about reporting  bugs,  can
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