.\" Copyright (c) 1985 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"	@(#)syslog.3	6.14 (Berkeley) %G%
.\"
.TH SYSLOG 3 ""
.UC 5
.SH NAME
syslog, vsyslog, openlog, closelog, setlogmask \- control system log
.SH SYNOPSIS
.nf
.ft B
#include <syslog.h>
syslog(int priority, char *message, [, arg ] ... );

include <varargs.h>
vsyslog(int priority, char *message, va_list args);

openlog(char *ident, int logopt, int facility);

closelog(void);

setlogmask(int maskpri);
.ft R
.fi
.SH DESCRIPTION
.I Syslog
writes
.I message
to the system message logger.
The message will then be written to the system console, log files,
logged-in users, or forwarded to other machines as appropriate (see
.IR syslogd (8)).
.PP
The message is identical to a
.IR printf (3)
format string, except that ``%m'' is replaced by the current error
message (as denoted by
.IR errno ;
see
.IR strerror (3)).
A trailing newline is added if none is present.
.PP
.I Vsyslog
is an alternate form in which the arguments have already been captured
using the variable-length argument facilities of
.IR varargs (3).
.PP
The message is tagged with
.IR priority .
Priorities are encoded as a
.I facility
and a
.IR level .
The facility describes the part of the system
generating the message.
The level is selected from the following
.B ordered
(high to low) list:
.TP
LOG_EMERG
A panic condition.
This is normally broadcast to all users.
.TP
LOG_ALERT
A condition that should be corrected immediately, such as a corrupted
system database.
.TP
LOG_CRIT
Critical conditions, e.g., hard device errors.
.TP
LOG_ERR
Errors.
.TP
LOG_WARNING
Warning messages.
.TP
LOG_NOTICE
Conditions that are not error conditions,
but should possibly be handled specially.
.TP
LOG_INFO
Informational messages.
.TP
LOG_DEBUG
Messages that contain information
normally of use only when debugging a program.
.PP
.I Openlog
provides for more specialized processing of the messages sent
by
.I syslog
and
.IR vsyslog .
The parameter
.I ident
is a string that will be prepended to every message.
.I Logopt
is a bit field specifying logging options, which is formed by
.IR OR 'ing
one or more of the following values:
.TP
LOG_CONS
If
.I syslog
cannot pass the message to
.I syslogd
it will attempt to write the message to the console (``/dev/console'').
.TP
LOG_NDELAY 
Open the connection to
.I syslogd
immediately.
Normally the open is delayed until the first message is logged.
Useful for programs that need to manage the order in which file
descriptors are allocated.
.TP
LOG_PERROR
Write the message to standard error output as well to the system log.
.TP
LOG_PID
Log the process id with each message: useful for identifying
instantiations of daemons.
.PP
The
.I facility
parameter encodes a default facility to be assigned to all messages
that do not have an explicit facility encoded:
.TP
LOG_AUTH
The authorization system:
.IR login (1),
.IR su (1),
.IR getty (8),
etc.
.TP
LOG_AUTHPRIV
The same as LOG_AUTH, but logged to a file readable only by
selected individuals.
.TP
LOG_CRON
The clock daemon.
.TP
LOG_DAEMON
System daemons, such as
.IR ftpd (8),
.IR routed (8),
etc., that are not provided for explicitly by other facilities.
.TP
LOG_KERN
Messages generated by the kernel.
These cannot be generated by any user processes.
.TP
LOG_LPR
The line printer spooling system:
.IR lpr (1),
.IR lpc (8),
.IR lpd (8),
etc.
.TP
LOG_MAIL
The mail system.
.TP
LOG_NEWS
The network news system.
.TP
LOG_SYSLOG
Messages generated internally by
.IR syslogd (8).
.TP
LOG_USER
Messages generated by random user processes.
This is the default facility identifier if none is specified.
.TP
LOG_UUCP
The uucp system.
.TP
LOG_LOCAL0
Reserved for local use.
Similarly for LOG_LOCAL1 through LOG_LOCAL7.
.PP
.I Closelog
can be used to close the log file.
.PP
.I Setlogmask
sets the log priority mask to
.I maskpri
and returns the previous mask.
Calls to
.I syslog
with a priority not set in
.I maskpri
are rejected.
The mask for an individual priority
.I pri
is calculated by the macro ``LOG_MASK(pri);''
the mask for all priorities up to and including
.I toppri
is given by the macro ``LOG_UPTO(toppri);''.
The default allows all priorities to be logged.
.SH EXAMPLES
.nf
.RS
syslog(LOG_ALERT, "who: internal error 23");

openlog("ftpd", LOG_PID, LOG_DAEMON);
setlogmask(LOG_UPTO(LOG_ERR));
syslog(LOG_INFO, "Connection from host %d", CallingHost);

syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");
.RE
.fi
.SH RETURNS
The routines
.I closelog ,
.I openlog ,
.I syslog
and
.I vsyslog
return 0 upon successful completion.
Otherwise, -1 is returned and
.I errno
is set to indicate the error.
.PP
The routine
.I setlogmask
always returns the previous log mask level, never returning
an error.
.SH ERRORS
The routines
.I syslog
and
.I vsyslog
may fail and set errno for any of the errors specified for the library
routines
.IR connect (2),
.IR send (2) ,
and
.IR socket (2).
.PP
The routine
.I openlog
may fail and set errno for any of the errors specified for the library
routines
.IR connect (2)
and
.IR socket (2).
.PP
The routine
.I closelog
may fail and set errno for any of the errors specified for the library
routine
.IR close (2).
.SH "SEE ALSO"
logger(1), syslogd(8)