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 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
       message 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,
       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(P)