SYSLOG(3)                      Library Routines                      SYSLOG(3)




NAME

       syslog,  vsyslog,  syslogmt, vsyslogmt, openlog, closelog, setlogmask -
       control system log


SYNOPSIS

       #include <stdarg.h>
       #include <syslog.h>

       void syslog (int priority, const char *message, ...);
       void vsyslog (int priority, const char *message, va_list args);
       void syslogmt (int priority, const char *message, ...);
       void vsyslogmt (int priority, const char *message, va_list args);
       void openlog (const char *ident, int logopt, int facility);
       void closelog (void);
       int setlogmask (int maskpri);


DESCRIPTION

       The syslog function writes message to the system message  logger.   The
       message  is  then  written  to the system console, log files, logged-in
       users, or forwarded to other machines as appropriate. (See syslogd(8).)

       The  message  is identical to a printf(3) format string, except that %m
       is replaced by the current error message. (As  denoted  by  the  global
       variable  errno; see strerror(3).)  A trailing newline is added if none
       is present.

       The vsyslog function is an alternate form in which the  arguments  have
       already  been captured using the variable-length argument facilities of
       varargs(3).

       The syslogmt and vsyslogmt are multithread-safe variants of the  syslog
       and  vsyslog routines.  Note that the permissable list of format speci-
       fiers for these two routines is much smaller than those for  syslog  or
       vsyslog.    The  full  list  of  format  specifiers  is  given  in  the
       sprintmt(3) manual page.  Note that syslogmt and vsyslogmt will not log
       to  syslogd(8)  unless  openlog  has been called.  Since openlog is not
       itself thread safe, the call to openlog must be made before the process
       forks if any children will be using these routines.  These two routines
       are GNO-specific and therefore non-portable.

       The message is tagged with  priority.   Priorities  are  encoded  as  a
       facility  and  a  level.  The facility describes the part of the system
       generating the message.  The  level  is  selected  from  the  following
       ordered (high to low) list:

              LOG_EMERG
                     A  panic  condition.   This  is normally broadcast to all
                     users.

              LOG_ALERT
                     A condition that should be corrected immediately, such as
                     a corrupted system database.

              LOG_CRIT
                     Critical conditions, e.g., hard device errors.

              LOG_ERR
                     Errors.

              LOG_WARNING
                     Warning messages.

              LOG_NOTICE
                     Conditions that are not error conditions, but should pos-
                     sibly be handled specially.

              LOG_INFO
                     Informational messages.

              LOG_DEBUG
                     Messages that contain information normally  of  use  only
                     when debugging a program.

       The  openlog  function  provides for more specialized processing of the
       messages sent by syslog and vsyslog.  The parameter ident is  a  string
       that  will be prepended to every message.  The logopt argument is a bit
       field specifying logging options, which is formed by OR'ing one or more
       of the following values:

              LOG_CONS
                     If  syslog  cannot pass the message to syslogd(8) it will
                     attempt to write the message to the console .ttyco.

              LOG_NDELAY
                     Open the connection to syslogd(8) immediately.   Normally
                     the  open  is  delayed until the first message is logged.
                     Useful for programs that need  to  manage  the  order  in
                     which file descriptors are allocated.

              LOG_PERROR
                     Write the message to standard error output as well to the
                     system log.

              LOG_PID
                     Log the process id with each message: useful for  identi-
                     fying instantiations of daemons.

       The facility parameter encodes a default facility to be assigned to all
       messages that do not have an explicit facility encoded:

              LOG_AUTH
                     The authorization system: login(1), su(1), getty(8), etc.

              LOG_AUTHPRIV
                     The  same as LOG_AUTH, but logged to a file readable only
                     by selected individuals.

              LOG_CRON
                     The cron daemon: cron(8).

              LOG_DAEMON
                     System daemons, such as routed(8), that are not  provided
                     for explicitly by other facilities.

              LOG_FTP
                     The file transfer protocol daemon: ftpd(8).

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

              LOG_LPR
                     The line printer spooling system: lpr(1), lpc(8), lpd(8),
                     etc.

              LOG_MAIL
                     The mail system.

              LOG_NEWS
                     The network news system.

              LOG_SYSLOG
                     Messages generated internally by syslogd(8).

              LOG_USER
                     Messages generated by random user processes.  This is the
                     default facility identifier if none is specified.

              LOG_UUCP
                     The uucp system.

              LOG_LOCAL0
                     Reserved for local use.  Similarly for LOG_LOCAL1 through
                     LOG_LOCAL7.

       The closelog function can be used to close the log file.

       The  setlogmask  function  sets  the  log  priority mask to maskpri and
       returns the previous mask.  Calls to syslog with a priority not set  in
       maskpri  are rejected.  The mask for an individual priority pri is cal-
       culated by the macro LOG_MASK(pri); the mask for all priorities  up  to
       and  including  toppri  is  given  by the macro LOG_UPTO(toppri);.  The
       default allows all priorities to be logged.


RETURN VALUES

       The routines closelog, openlog, syslog and vsyslog return no value.

       The routine setlogmask always returns the previous log mask level.


EXAMPLES

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

       openlog("ftpd", LOG_PID | LOG_NDELAY, LOG_FTP);

       setlogmask(LOG_UPTO(LOG_ERR));

       syslog(LOG_INFO, "Connection from host %d", CallingHost);

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


MT STATUS

       syslogmt and vsyslogmt are thread safe; the remainder are not.  openlog
       should  be  called  in  the  parent  thread  before  creating the child
       threads.  This will ensure that any  generated  messages  are  properly
       tagged with ident.


BUGS

       The  current  implementation does not take into account the possibility
       that syslogd(8) may be killed and restarted.  If this happens, all log-
       ging  from  the  current  process  will  stop  until  a call is made to
       closelog followed by openlog, which is of course not thread safe.  This
       could be handled better.


SEE ALSO

       logger(1), sprintmt(3), syslogd(8)


HISTORY

       These functions appeared in 4.2BSD.



GNO                             4 January 1999                       SYSLOG(3)

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