SYSLOG(3) closelog, openlog, syslog - send messages to the system logger #includevoid openlog(const char *ident, int option, int facility); void syslog(int priority, const char *format, ...); void closelog(void); #include void vsyslog(int priority, const char *format, va_list ap); closelog() closes the descriptor being used to write to the system logger. optional. openlog() opens a connection to the system logger for a program. The string pointed to by ident is prepended to every message, and is typically set to the program name. The option argument specifies flags which control the operation of openlog() and subsequent calls to syslog(). The facility argument establishes a default to be used if none is specified in subsequent calls to syslog(). Values for option and facility are given below. The use of openlog() is optional; it will automatically be called by syslog() if necessary, in which case ident will default to NULL. syslog() generates a log message, which will be distributed by syslogd(8). The priority argument is formed by ORing the facility and the level values. The remaining arguments are a format, as in printf(3) and any arguments required by the format, except that the two character sequence %m will be replaced by the error message string strerror(errno). A trailing newline is added when needed. vsyslog() performs the same task as syslog() with the difference that it takes a set of arguments which have been obtained using the stdarg(3) variable argument list macros. PARAMETERS used to set the values of option, facility, and priority. option The option argument to openlog() is an OR of any of these: LOG_CONS Write directly to system console if there is an error while sending to system logger. LOG_NDELAY Open the connection immediately (normally, the connection is opened when the first message is logged). LOG_ODELAY The converse of LOG_NDELAY; opening of the connection is delayed until syslog() is called. (default, LOG_NOWAIT Don't wait for child processes that may have been created while logging the message. LOG_PERROR Print to stderr as well. LOG_PID Include PID with each message. facility The facility argument is used to specify what type of program is logging the message. This lets the configuration file specify that messages from different facilities will be handled differently. RFC 5424 Numerical Facility Code 0 kernel messages LOG_KERN 1 user-level messages 2 mail system LOG_MAIL 3 system daemons 4 security/authorization messages 5 messages generated internally by syslogd 6 line printer subsystem LOG_LPR 7 network news subsystem LOG_NEWS USENET news subsystem 8 UUCP subsystem LOG_UUCP 9 clock daemon LOG_CRON (cron and at) 10 security/authorization messages 11 FTP daemon LOG_FTP 12 NTP subsystem 13 log audit 14 log alert 15 clock daemon (note 2) 16 local use 0 (local0) 17 local use 1 (local1) 18 local use 2 (local2) 19 local use 3 (local3) 20 local use 4 (local4) 21 local use 5 (local5) 22 local use 6 (local6) 23 local use 7 (local7) LOG_AUTH security/authorization messages (DEPRECATED Use LOG_AUTHPRIV instead) LOG_AUTHPRIV security/authorization messages (private) LOG_DAEMON system daemons without separate facility value LOG_KERN LOG_LOCAL0 through LOG_LOCAL7 for local use LOG_SYSLOG internally by syslogd LOG_USER (default) generic user-level messages apple permits any value for the "Facility" ( man syslogd) only processes running with UID 0 may log messages with a facility value of "com.apple.system", or with a value that has "com.apple.system" as a prefix. Messages logged by non UID 0 processes that use "com.apple.system" as a facility value or prefix will be saved with the facility value "user". level This determines the importance of the message. Order in decreasing importance: 0 LOG_EMERG system is unusable 1 LOG_ALERT action must be taken immediately 2 LOG_CRIT critical 3 LOG_ERR 4 LOG_WARNING 5 LOG_NOTICE normal, but significant, condition 6 LOG_INFO 7 LOG_DEBUG "<"Facility*8+sev">" Example <0> KERN+EM; The function setlogmask(3) can be used to restrict logging to specified levels only. The parameter ident in the call of openlog() is probably stored as-is. if the string it points to is changed, syslog() may start prepending the changed string, and if the string it points to ceases to exist, the results are undefined. Most portable is to use a string constant. Never pass a string with user-supplied data as a format, use syslog("%s", string); SEE ALSO logger(1), setlogmask(3), syslog.conf(5), syslogd(8)