5 library(syslog): Unix syslog interface

See also

- detach_IO/1 to detach normal I/O of the process and remove it from the process group.
- fork/1 to create a daemon process.
- library(uid) to manage user identifiers (e.g., drop root privileges).

This library provides an interface to the Unix syslog() facility. The interface is an almost direct translation of the POSIX syslog API, with two additions:

• syslog/3 exploits format/3 to format syslog messages
• The library integrates into library(debug) using prolog:debug_print_hook/3, where debug topics are mapped to syslog priorities and remaining debug topics are mapped to the syslog priority debug.

Note that this interface makes no attempt to abstract over logging facilities of operating systems. We expect that such abstractions will be implemented at the Prolog level using multiple integrations into library(debug).

[det]openlog(+Ident:atom, +Options:list(atom), +Facility:atom)

Open system log. This predicate provides a direct interface into the openlog() library call. If the library call is successful, it runs at_halt(closelog) to ensure closing the system log on clean exit.

Ident	prepended to every message, and is typically set to the program name.
Options	is a list of options. Values are corresponding C options, after removing =LOG_= and translation to lower case: cons, ndelay, nowait, odelay, perror, pid.
Facility	is one of auth, authpriv, cron, daemon, ftp, kern, local0 ... local7, lpr, mail, news, syslog, user or uucp.

[det]syslog(+Priority, +Message)

Send a message to the system log. Note that syslog/2 implicitly opens a connection to the system log if such a connection has not been opened explicitly using openlog/3.

Priority

is one of emerg, alert, crit, err, warning, notice, info or debug.

[det]syslog(+Priority, +Format, +Args)

Send a formatted message to the system log if system logging is opened using openlog/3. This predicate combined format/3 with syslog/2. If there is no open syslog connection, syslog/3 calls print_message/2.

[det]closelog

Close the system log.

[semidet,multifile]prolog:debug_print_hook(+Topic, +Format, +Args)

Integration of debug/3 with the syslog facility. If syslog is enabled, debug/3 is re-routed to use the syslog facilities. If the topic of the debug message matches one of the sylog priority values (see syslog/2), the message is sent with the corresponding syslog priority. Otherwise it it sent with the debug priority.