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closelog, openlog, syslog – send messages to the system
void openlog( char *ident, int option, int facility)
void syslog( int priority, char *format, …)
void closelog( void )
closelog() closes the descriptor being used to write to
the system logger. The use of closelog() is optional.
openlog() opens a connection to the system logger for a
program. The string pointed to by ident is added to each
message, and is typically set to the program name. Values
for option and facility are given in the next section.
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 dis-
tributed by syslogd(8). priority is a combination of the
facility and the level, values for which are given in the
next section. The remaining arguments are a format, as in
printf(3) and any arguments required by the format, except
that the two character %m will be replaced by the error
message string (strerror) corresponding to the present
value of errno.
This section lists the parameters used to set the values
of option, facility, and priority.
The option argument to openlog() is an OR of any of these:
write directly to system console if there is an
error while sending to system logger
open the connection immediately (normally, the con-
nection is opened when the first message is logged)
print to stderr as well
include PID with each message
The facility argument is used to specify what type of pro-
gram is logging the message. This lets the configuration
file specify that messages from different facilities will
be handled differently.
security/authorization messages (DEPRECATED Use
security/authorization messages (private)
clock daemon (cron and at)
other system daemons
LOG_LOCAL0 through LOG_LOCAL7
reserved for local use
line printer subsystem
USENET news subsystem
messages generated internally by syslogd
generic user-level messages
This determines the importance of the message. The levels
are, in order of decreasing importance:
system is unusable
action must be taken immediately
normal, but significant, condition
A syslog function call appeared in BSD 4.2.
logger(1), syslog(5), syslogd(8)