.\" Written  Feb 1994 by Steve Greenland (stevegr@neosoft.com)
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.TH SYSLOG 3 "15 Feb 1994" "Linux" "Linux Programmer's Manual"
.SH NAME
closelog, openlog, syslog \- send messages to the system logger
.SH SYNOPSIS
.B #include <syslog.h>
.sp
.BI "void openlog( char " *ident ", int " option ", int  " facility )
.sp
.BI "void syslog( int " priority ", char " *format ", ...)"
.sp
.BI "void closelog( void )"
.sp
.SH DESCRIPTION
.B closelog()
closes the descriptor being used to write to the system logger.  The use of
.B closelog()
is optional.
.sp
.B openlog()
opens a connection to the system logger for a program.  The string pointed
to by
.I ident 
is added to each message, and is typically set to the program name.  Values for
.I option
and
.I facility
are given in the next section.  The use of 
.B openlog()
is optional; It will automatically be called by 
.B syslog()
if necessary, in which case 
.I ident
will default to NULL.
.sp
.B syslog()
generates a log message, which will be distributed by 
.BR syslogd (8).
.I priority
is a combination of the
.I facility
and the 
.IR level , 
values for which are given in the next section.  The remaining arguments
are a 
.IR format ,
as in 
.BR printf (3)
and any arguments required by the 
.IR format , 
except that the two character %m will be replaced by the error message 
string 
.RI ( strerror )
corresponding to the present value of 
.IR errno .

.SH "PARAMETERS"
This section lists the parameters used to set the values of 
.IR option , " facility" ", and " priority .
.SS option
The
.I option
argument to 
.B openlog()
is an OR of any of these:
.TP
.B LOG_CONS
write directly to system console if there is an error while sending to
system logger
.TP
.B LOG_NDELAY
open the connection immediately (normally, the connection is opened when
the first message is logged)
.TP
.B LOG_PERROR
print to stderr as well
.TP
.B LOG_PID
include PID with each message
.SS facility 
The 
.I 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.
.TP
.B LOG_AUTH
security/authorization messages (DEPRECATED Use 
.B LOG_AUTHPRIV 
instead)
.TP
.B LOG_AUTHPRIV
security/authorization messages (private) 
.TP
.B LOG_CRON
clock daemon 
.RB ( cron " and " at )
.TP
.B LOG_DAEMON
other system daemons
.TP
.B LOG_KERN
kernel messages
.TP
.BR LOG_LOCAL0 " through " LOG_LOCAL7
reserved for local use
.TP
.B LOG_LPR
line printer subsystem
.TP
.B LOG_MAIL
mail subsystem
.TP
.B LOG_NEWS
USENET news subsystem
.TP
.B LOG_SYSLOG
messages generated internally by
.B syslogd 
.TP
.BR LOG_USER (default)
generic user-level messages 
.TP
.B LOG_UUCP
UUCP subsystem

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


.SH HISTORY
A
.B syslog
function call appeared in BSD 4.2.
.SH SEE ALSO
.BR logger "(1), " syslog.conf "(5), " syslogd (8)