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syslog(3c)

Standard C Library Functions                                        syslog(3C)



NAME
       syslog, openlog, closelog, setlogmask - control system log

SYNOPSIS
       #include <syslog.h>

       void openlog(const char *ident, int logopt, int facility);


       void syslog(int priority, const char *message, .../* arguments */);


       void closelog(void);


       int setlogmask(int maskpri);

DESCRIPTION
       The  syslog()  function sends a message to syslogd(8), which, depending
       on the configuration of /etc/syslog.conf, logs  it  in  an  appropriate
       system  log,  writes it to the system console, forwards it to a list of
       users, or forwards it to syslogd on another host over the network.  The
       logged  message  includes a message header and a message body. The mes‐
       sage header consists of a facility indicator, a severity level  indica‐
       tor, a timestamp, a tag string, and optionally the process ID.


       The  message body is generated from the message and following arguments
       in the same manner as if these were  arguments  to  printf(3C),  except
       that  occurrences  of %m in the format string pointed to by the message
       argument are replaced by the error message string associated  with  the
       current  value  of  errno.  A  trailing  NEWLINE  character is added if
       needed.


       Symbolic constants for use as values of the logopt, facility, priority,
       and maskpri arguments are defined in the <syslog.h> header.


       Values of the priority argument are formed by ORing 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, in decreasing order:

       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, 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_KERN      Messages generated by the kernel. These cannot be  gener‐
                     ated by any user processes.


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


       LOG_MAIL      The mail system.


       LOG_DAEMON    System daemons.


       LOG_AUTH      The authentication /  security  /  authorization  system:
                     login(1), su(8), getty(8).


       LOG_NEWS      Designated for the USENET network news system.


       LOG_UUCP      Designated for the UUCP system; it does not currently use
                     syslog().


       LOG_CRON      The cron/at facility; crontab(1), at(1), cron(8).


       LOG_AUDIT     The audit facility, for example, auditd(8).


       LOG_LOCAL0    Designated for local use.


       LOG_LOCAL1    Designated for local use.


       LOG_LOCAL2    Designated for local use.


       LOG_LOCAL3    Designated for local use.


       LOG_LOCAL4    Designated for local use.


       LOG_LOCAL5    Designated for local use.


       LOG_LOCAL6    Designated for local use.


       LOG_LOCAL7    Designated for local use.



       The openlog() function sets process attributes that  affect  subsequent
       calls  to syslog(). The ident argument is a string that is prepended to
       every message. The openlog() function uses the passed-in ident argument
       directly,  rather than making a private copy of it. The logopt argument
       indicates logging options. Values for logopt are constructed by a  bit‐
       wise-inclusive OR of zero or more of the following:

       LOG_PID       Log  the process ID with each message. This is useful for
                     identifying specific daemon processes (for  daemons  that
                     fork).


       LOG_CONS      Write  messages  to  the system console if they cannot be
                     sent to syslogd(8). This option is safe to use in  daemon
                     processes  that  have no controlling terminal, since sys‐
                     log() forks before opening the console.


       LOG_NDELAY    Open the connection to syslogd(8)  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 have been forked to
                     log messages onto the console. This option should be used
                     by  processes  that enable notification of child termina‐
                     tion 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 closes any open file descriptors allocated by
       previous calls to openlog() or syslog().


       The setlogmask() function sets the log priority mask  for  the  current
       process  to maskpri and returns the previous mask. If the maskpri argu‐
       ment is 0, the current log mask is not modified. Calls by  the  current
       process  to  syslog()  with a priority not set in maskpri are rejected.
       The mask for an individual priority pri  is  calculated  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 log mask allows all
       priorities to be logged.

RETURN VALUES
       The  setlogmask()  function returns the previous log priority mask. The
       closelog(), openlog() and syslog() functions return no value.

ERRORS
       No errors are defined.

EXAMPLES
       Example 1 Example of LOG_ALERT message.




       This call logs a message at priority LOG_ALERT:


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




       The FTP daemon ftpd would make this call to openlog() to indicate  that
       all  messages it logs should have an identifying string of ftpd, should
       be treated by syslogd(8) as other messages  from  system  daemons  are,
       should include the process ID of the process logging the message:


         openlog("ftpd", LOG_PID, LOG_DAEMON);




       Then  it would make the following call to setlogmask() to indicate that
       messages at priorities from LOG_EMERG through LOG_ERR should be logged,
       but that no messages at any other priority should be logged:


         setlogmask(LOG_UPTO(LOG_ERR));




       Then,  to log a message at priority LOG_INFO, it would make the follow‐
       ing call to syslog:


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




       A locally-written utility could use the following call to  syslog()  to
       log a message at priority LOG_INFO to be treated by syslogd(8) as other
       messages to the facility LOG_LOCAL2 are:


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



ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE VALUE _ Interface StabilityCommitted _ MT-LevelSafe _ Standard‐
       See standards(7).


SEE ALSO
       at(1), crontab(1),  logger(1),  login(1),  printf(3C),  syslog.conf(5),
       attributes(7),  standards(7), auditd(8), cron(8), getty(8), su(8), sys‐
       logd(8)



Oracle Solaris 11.4               16 Aug 2011                       syslog(3C)
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