syslog, openlog, closelog, setlogmask

Purpose

     Makes a system log entry.

Library

     Berkeley Library (libbsd.a)

Syntax

     #include <bsd/sys/syslog.h>

     void syslog (priority, message [, val, ...void closelog ( )
     int priority;
     char *message;                            int setlogmask (maskpri)
                                               int maskpri;
     void openlog (ident, logopt, facility)
     char *ident;
     int logopt, facility;
     Description

     The syslog subroutine writes messages onto the system log
     maintained by the syslogd.  The message string is similar
     to the printf  fmt string, with the  difference that" %m"
     is replaced  by the  current error message  obtained from
     errno.  A trailing  new line can be added  to the message
     if needed.   The val parameters  are the same as  the val
     parameters of the printf subroutine.

     Messages  are read  by  the syslogd  and  written to  the
     system console or  log file, or forwarded  to the syslogd
     on the appropriate host.

     Messages  are tagged  with codes  indicating the  type of
     priority for each.  A priority  is encoded as a facility,
     which  describes the  part of  the system  generating the
     message, and as a level,  which indicates the severity of
     the message.

     The facility  that generated  the message  is one  of the
     following:

     LOG_KERN     Messages  generated  by the  kernel.   These
                  cannot be generated by any user processes.

     LOG_USER     Messages generated by  user processes.  This
                  is the default facility  when none is speci-
                  fied.

     LOG_MAIL     The mail system.

     LOG_DAEMON   System daemons.

     LOG_AUTH     The authorization system:  login, su, and so
                  on.

     LOG_LPR      The line printer spooling system.

     LOG_LOCAL0   Reserved for local use.
     through
     LOG_LOCAL7

     The  level of  severity  is selected  from the  following
     list:

     LOG_EMERG     A panic condition reported to all users.

     LOG_ALERT     A condition that  should be corrected imme-
                   diately; for example, a corrupted database.

     LOG_CRIT      Critical  conditions:   for  example,  hard
                   device errors.

     LOG_ERR       Errors.

     LOG_WARNING   Warning messages.

     LOG_NOTICE    Not  an error  condition,  but a  condition
                   requiring special handling.

     LOG_INFO      General information messages.

     LOG_DEBUG     Messages  containing information  useful to
                   debug a program.

     If syslog cannot  pass the message to  syslogd, it writes
     the message on /dev/console, provided the LOG_CONS option
     is set.

     Note:  Since AIX  does not create file  names for AF_UNIX
     sockets,  there  is no  /dev/log  file  created when  the
     syslogd is  started.  A program  therefore has no  way to
     find out if the syslogd  is running, unless it checks the
     process ID contained in /etc/syslog.pid.

     If special processing is required, the openlog subroutine
     can be used to initialize the log file.  The ident param-
     eter contains a string that  is attached to the beginning
     of  every  message.   The facility  parameter  encodes  a
     default facility from the previous list to be assigned to
     messages that do not have an explicit facility encoded.

     The  logopt  parameter  is  a bit  field  that  indicates
     logging options.  The values of logopt include:

     LOG_PID      Log the process ID  with each message.  This
                  option is useful for identifying daemons.

     LOG_CONS     Send messages  to the  console if  unable to
                  send them to syslogd.  This option is useful
                  in daemon processes that have no controlling
                  terminal.

     LOG_NDELAY   Open the connection  to syslogd immediately,
                  instead of when the first message is logged.
                  This option is useful for programs that need
                  to manage  the order in which  file descrip-
                  tors are allocated.

     LOG_NOWAIT   Log messages to  the console without waiting
                  for  forked children.   Use this  option for
                  processes that enable  notification of child
                  termination   through  SIGCHLD;   otherwise,
                  syslog may block, waiting  for a child whose
                  exit status has already been collected.

     The closelog subroutine closes the log file.

     The setlogmask subroutine uses the bit mask in maskpri to
     set the  new log priority  mask and returns  the previous
     mask.  Logging is enabled for the levels indicated by the
     bits in the mask that are set and disabled where the bits
     are not set.   The default mask allows  all priorities to
     be logged.

     The LOG_MASK and LOG_UPTO  macros in the bsd/sys/syslog.h
     file  are used  to create  the priority  mask.  Calls  to
     syslog with a  priority mask that does  not allow logging
     of that particular level of message, cause the subroutine
     to return without logging the message.

     Examples

       syslog (LOG_ALERT, "who:internal error 23");

       openlog ("ftpd", LOG_PID, LOG_DAEMON);
       setlogmask (LOG_UPTO (LOG_ERR));
       syslog (LOG_INFO, "Connection from host %d", CallingHost);

       syslog (LOG_INFO|LOG_LOCAL2, "foobar error:%m");

     Related Information

     In  this  book:   "printf,  fprintf,  sprintf,  NLprintf,
     NLfprintf, NLsprintf."

     The discussion  of syslogd  in AIX Operating  System Com-
     mands Reference.