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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 dif-
       fer (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 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  argu-
       ment  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()  func-
              tion  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  sys-
       log().

       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 console 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  mes-
       sage as an error message generated 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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)