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CLOSELOG(3P)               POSIX Programmer's Manual              CLOSELOG(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       closelog, openlog, setlogmask, syslog - control system log
SYNOPSIS
       #include <syslog.h>
       void closelog(void);
       void openlog(const char *ident, int logopt, int facility);
       int setlogmask(int maskpri);
       void syslog(int priority, const char *message, ... /* arguments */);

DESCRIPTION
       The syslog() function shall send a message to an implementation-defined
       logging  facility, which may log it in an implementation-defined system
       log, write it to the system console, forward it to a list of users,  or
       forward  it  to  the logging facility on another host over the network.
       The logged message shall include a message header and a  message  body.
       The message header contains at least a timestamp and a tag string.
       The  message body is generated from the message and following arguments
       in the same manner as if these were arguments to printf(), except  that
       the  additional  conversion  specification  %m  shall be recognized; it
       shall convert no arguments, shall cause the output of the error message
       string associated with the value of errno on entry to syslog(), and may
       be mixed with argument specifications of the "%n$" form.  If a complete
       conversion  specification  with the m conversion specifier character is
       not just %m, the behavior is undefined. A  trailing  <newline>  may  be
       added if needed.
       Values  of the priority argument are formed by OR'ing together a sever-
       ity-level value and an optional facility value. If no facility value is
       specified, the current default facility value is used.
       Possible values of severity level include:
       LOG_EMERG
              A panic condition.
       LOG_ALERT
              A condition that should be corrected immediately, such as a cor-
              rupted system database.
       LOG_CRIT
              Critical conditions, such as hard device errors.
       LOG_ERR
              Errors.
       LOG_WARNING
              Warning messages.
       LOG_NOTICE
              Conditions that are not error conditions, but that  may  require
              special handling.
       LOG_INFO
              Informational messages.
       LOG_DEBUG
              Messages  that  contain  information  normally  of use only when
              debugging a program.

       The facility indicates the application or system  component  generating
       the message. Possible facility values include:
       LOG_USER
              Messages  generated  by arbitrary processes. This is the default
              facility identifier if none is specified.
       LOG_LOCAL0
              Reserved for local use.
       LOG_LOCAL1
              Reserved for local use.
       LOG_LOCAL2
              Reserved for local use.
       LOG_LOCAL3
              Reserved for local use.
       LOG_LOCAL4
              Reserved for local use.
       LOG_LOCAL5
              Reserved for local use.
       LOG_LOCAL6
              Reserved for local use.
       LOG_LOCAL7
              Reserved for local use.

       The openlog() function shall set process attributes that affect  subse-
       quent  calls  to  syslog().  The  ident  argument  is  a string that is
       prepended to every  message.  The  logopt  argument  indicates  logging
       options. Values for logopt are constructed by a bitwise-inclusive OR of
       zero or more of the following:
       LOG_PID
              Log the process ID with each message. This is useful for identi-
              fying specific processes.
       LOG_CONS
              Write  messages  to the system console if they cannot be sent to
              the logging facility. The syslog()  function  ensures  that  the
              process  does  not acquire the console as a controlling terminal
              in the process of writing the message.
       LOG_NDELAY
              Open the connection to the logging  facility  immediately.  Nor-
              mally  the  open  is  delayed until the first message is logged.
              This is useful for programs that need to  manage  the  order  in
              which file descriptors are allocated.
       LOG_ODELAY
              Delay open until syslog() is called.
       LOG_NOWAIT
              Do  not wait for child processes that may have been created dur-
              ing the course of logging the message.  This  option  should  be
              used  by processes that enable notification of child termination
              using SIGCHLD, since syslog() may otherwise block waiting for  a
              child whose exit status has already been collected.

       The  facility argument encodes a default facility to be assigned to all
       messages that do not have an explicit  facility  already  encoded.  The
       initial default facility is LOG_USER.
       The openlog() and syslog() functions may allocate a file descriptor. It
       is not necessary to call openlog() prior to calling syslog().
       The closelog() function shall close any open file descriptors allocated
       by previous calls to openlog() or syslog().
       The  setlogmask() function shall set the log priority mask for the cur-
       rent process to maskpri and return the previous mask.  If  the  maskpri
       argument  is 0, the current log mask is not modified. Calls by the cur-
       rent process to syslog() with a priority not set in  maskpri  shall  be
       rejected.   The  default log mask allows all priorities to be logged. A
       call to openlog() is not required prior to calling setlogmask().
       Symbolic constants for use as values of the logopt, facility, priority,
       and maskpri arguments are defined in the <syslog.h> header.
RETURN VALUE
       The  setlogmask() function shall return the previous log priority mask.
       The closelog(), openlog(), and syslog() functions shall  not  return  a
       value.
ERRORS
       No errors are defined.
       The following sections are informative.
EXAMPLES
   Using openlog()
       The  following  example  causes subsequent calls to syslog() to log the
       process ID with each message, and to write messages to the system  con-
       sole if they cannot be sent to the logging facility.

              #include <syslog.h>

              char *ident = "Process demo";
              int logopt = LOG_PID | LOG_CONS;
              int facility = LOG_USER;
              ...
              openlog(ident, logopt, facility);
   Using setlogmask()
       The  following  example  causes  subsequent calls to syslog() to accept
       error messages, and to reject all other messages.

              #include <syslog.h>

              int result;
              int mask = LOG_MASK (LOG_ERR);
              ...
              result = setlogmask(mask);
   Using syslog
       The following example sends the message "This  is  a  message"  to  the
       default  logging facility, marking the message as an error message gen-
       erated by random processes.

              #include <syslog.h>

              char *message = "This is a message";
              int priority = LOG_ERR | LOG_USER;
              ...
              syslog(priority, message);
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       printf(), the Base Definitions volume  of  IEEE Std 1003.1-2001,  <sys-
       log.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                         CLOSELOG(3P)