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SYSLOG(3) Linux Programmer's Manual SYSLOG(3)

NAME

closelog, openlog, syslog - send messages to the system logger

SYNOPSIS

#include <syslog.h>

void openlog( char *ident, int option, int facility)

void syslog( int priority, char *format, ...)

void closelog( void )

DESCRIPTION

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 distributed 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.

PARAMETERS

This section lists the 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_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.
LOG_AUTH
security/authorization messages (DEPRECATED Use LOG_AUTHPRIV instead)
LOG_AUTHPRIV
security/authorization messages (private)
LOG_CRON
clock daemon (cron and at)
LOG_DAEMON
other system daemons
LOG_KERN
kernel messages
LOG_LOCAL0 through 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(default)
generic user-level messages
LOG_UUCP
UUCP subsystem

level

This determines the importance of the message. The levels are, in order of decreasing importance:
LOG_EMERG
system is unusable
LOG_ALERT
action must be taken immediately
LOG_CRIT
critical conditions
LOG_ERR
error conditions
LOG_WARNING
warning conditions
LOG_NOTICE
normal, but significant, condition
LOG_INFO
informational message
LOG_DEBUG
debug-level message

HISTORY

A syslog function call appeared in BSD 4.2.

SEE ALSO

logger(1), syslog.conf(5), syslogd(8)
15 Feb 1994 Linux