openlog() opens a connection to the system logger for a program. The string ident is added to each message. Values for option and facility are given below. The option argument is used to indicate what loggin options will be used when generating a log message. The facility argument is used to specify what type of program is logging the message. This allows you to specify (in your machine's syslog configuration) how messages coming from different facilities will be handled. The use of openlog() is optional. It will automatically be called by syslog() if necessary, in which case ident will default to FALSE.
Table 1. openlog() Options
| Constant | Description |
|---|---|
| LOG_CONS | if there is an error while sending data to the system logger, write directly to the system console |
| LOG_NDELAY | open the connection to the logger immediately |
| LOG_ODELAY | (default) delay openning the connection until the first message is logged |
| LOG_PERROR | print log message also to standard error |
| LOG_PID | include PID with each message |
Table 2. openlog() Facilities
| Constant | Description |
|---|---|
| LOG_AUTH | security/authorization messages (use LOG_AUTHPRIV instead in systems where that constant is defined) |
| LOG_AUTHPRIV | security/authorization messages (private) |
| LOG_CRON | clock daemon (cron and at) |
| LOG_DAEMON | other system daemons |
| LOG_KERN | kernel messages |
| LOG_LOCAL0 ... LOG_LOCAL7 | reserved for local use |
| LOG_LPR | line printer subsystem |
| LOG_MAIL | mail subsystem |
| LOG_NEWS | USENET news subsystem |
| LOG_SYSLOG | messages generated internally by syslogd |
| LOG_USER | generic user-level messages |
| LOG_UUCP | UUCP subsystem |
See also define_syslog_variables(), syslog() and closelog().