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 correspond-
       ing 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 severity-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 corrupted 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 subsequent 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 identifying 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. Normally 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 during 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 current process to maskpri and return the previous mask. If the maskpri
       argument is 0, the current log mask is not modified. Calls by the current 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 gener-
       ated 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, <syslog.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- 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)