Provided by: manpages-dev_2.17-1_all bug

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  4.2BSD.   4.3BSD   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(priority, "%s", string);
       instead.

SEE ALSO

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