Module Syslog

module Syslog: sig .. end
Syslog Interface
Author(s): Markus Mottl <> Syslog is great for system daemons that log free-form human readable status messages or other debugging output, but not so great for archiving structured data. Access to read syslog's messages may also be restricted. syslogd's logs are also not necessarily kept forever. For application level logging consider the [Logger] module instead.

Options for opening syslog

type opt = 
| PID (*Include PID with each message*)
| CONS (*Write directly to system console if there is an error while sending to system logger*)
| ODELAY (*Delay opening of the connection until syslog is called*)
| NDELAY (*No delay opening connection to syslog daemon*)
| NOWAIT (*Do not wait for child processes while logging message*)
| PERROR (*Print to stderr as well*)

Types of syslog messages (facilities)

type fac = 
| KERN (*Kernel messages*)
| USER (*Generic user-level message (default)*)
| MAIL (*Mail subsystem*)
| DAEMON (*System daemons without separate facility value*)
| AUTH (*Security/authorization messages (DEPRECATED, use AUTHPRIV)*)
| SYSLOG (*Messages generated internally by syslogd*)
| LPR (*Line printer subsystem*)
| NEWS (*USENET news subsystem*)
| UUCP (*UUCP subsystem*)
| CRON (*Clock daemon (cron and at)*)
| AUTHPRIV (*Security/authorization messages (private)*)
| FTP (*FTP daemon*)
| LOCAL7 (*LOCAL0-7 reserved for local use*)

Types of and functions for logging levels

type lev = 
| EMERG (*System is unusable*)
| ALERT (*Action must be taken immediately*)
| CRIT (*Critical condition*)
| ERR (*Error conditions*)
| WARNING (*Warning conditions*)
| NOTICE (*Normal, but significant, condition*)
| INFO (*Informational message*)
| DEBUG (*Debug-level message*)
val all_levs : lev array
all_levs array of all logging levels sorted in ascending order.
val all_str_levs : string array
all_str_levs array of all logging levels as strings sorted in ascending order.
val compare_lev : lev -> lev -> int
compare_lev lev1 lev2 compares logging levels lev1 and lev2.
val string_of_lev : lev -> string
string_of_lev lev converts a level lev to a string.
val lev_of_string : string -> lev
lev_of_string str converts string str to a level.
Raises Failure if level does not exist.
val setlogmask : ?levs:lev list ->
?from_lev:lev -> ?to_lev:lev -> unit -> unit
setlogmask ?levs ?from_lev ?to_lev () sets the log mask. All levels in levs will be allowed, and additionally all ranging from from_lev to to_lev (inclusive).
levs : default = none
from_lev : default = DEBUG
to_lev : default = EMERG

Logging functions

val openlog : ?id:string -> ?opt:opt list -> ?fac:fac -> unit -> unit
openlog ?id ?opt ?fac () opens a connection to the system logger (possibly delayed) using prefixed identifier id, options opt, and faculty fac.

WARNING: this function leaks the id argument, if provided. No way around that if syslog is called in a multi-threaded environment! Therefore it shouldn't be called too often. What for, anyway?

id : default = Sys.argv.(0)
opt : default = ODELAY
fac : default = USER

Calling openlog before syslog is optional. If you forget, syslog will do it for you with the defaults.

val syslog : ?fac:fac -> ?lev:lev -> string -> unit
syslog ?fac ?lev str logs message str using syslog with faculty fac at level lev.
fac : default = as passed by openlog
lev : default = INFO
val esyslog : ?fac:fac -> ?lev:lev -> string -> unit
esyslog ?fac ?lev str same as Syslog.syslog, but also prints to stderr.
val syslogf : ?fac:fac ->
?lev:lev -> ('b, unit, string, unit) Pervasives.format4 -> 'b
syslog_printf ?fac ?lev fmt same as Syslog.syslog, but allows printf-style specification of the message using fmt.
val esyslogf : ?fac:fac ->
?lev:lev -> ('b, unit, string, unit) Pervasives.format4 -> 'b
esyslog_printf ?fac ?lev fmt same as Syslog.syslog_printf, but also prints to stderr.
val closelog : unit -> unit
closelog () closes the connection to the syslog daemon.