SYSLOG(3)SYSLOG(3)NAME
syslog, openlog, closelog, setlogmask, vsyslog - control
system log
SYNOPSIS
#include <syslog.h>
openlog(ident, logopt, facility)
char *ident;
syslog(priority, message, parameters ... )
int priority;
char *message;
#include <varargs.h>
vsyslog(priority, message, args)
int priority;
char *message;
va_list args;
closelog()setlogmask(maskpri)DESCRIPTION
Syslog arranges to write message onto the system log main-
tained by syslogd(8). The message is tagged with prior-
ity. The message looks like a printf(3) string except
that %m is replaced by the current error message (as ref-
erenced by errno). A trailing newline is added if needed.
An alternate form, in which the arguments have already
been captured using the variable-length argument facili-
ties of varargs(3), is available under the name vsyslog.
This message will be read by syslogd(8) and written to the
system console, log files, or forwarded to syslogd on
another host as appropriate.
Priorities are encoded as a facility and a level. The
facility describes the part of the system generating the
message. The level is selected from an ordered list:
LOG_ALERT
A condition that should be corrected immediately,
such as a corrupted system database.
LOG_CRIT
Critical conditions, e.g., hard device errors.
LOG_DEBUG
Messages that contain information normally of use
only when debugging a program.
LOG_EMERG
A panic condition. This is normally broadcast to
all users.
LOG_ERR
Errors.
LOG_INFO
Informational messages.
LOG_NOTICE
Conditions that are not error conditions, but
should possibly be handled specially.
LOG_WARNING
Warning messages.
If syslog cannot pass the message to syslogd, it will
attempt to write the message to the console (``/dev/con-
sole'') if the LOG_CONS option is set (see below).
If special processing is needed, openlog can be called to
initialize the log file. The parameter ident is a string
that is prepended to every message. Logopt is a bit field
indicating logging options. Current values for logopt
are:
LOG_CONS
If unable to send the message to syslogd, write it
to the console.
LOG_NDELAY
Open the connection to syslogd immediately. Nor-
mally 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.
LOG_PERROR
Write the message to stderr as well to the system
log.
LOG_PID
Log the process id with each message: useful for
identifying instantiations of daemons.
The facility parameter encodes a default facility to be
assigned to all messages that do not have an explicit
facility encoded:
LOG_AUTH
The authorization system: login(1), su(1),
getty(8), etc.
LOG_CRON
The clock daemon.
LOG_DAEMON
System daemons, such as ftpd(8), routed(8), etc,
that are not provided for explicitly by other
facilities.
LOG_KERN
Messages generated by the kernel. These cannot be
generated by any user processes.
LOG_LPR
The line printer spooling system: lpr(1), lpc(8),
lpd(8), etc.
LOG_MAIL
The mail system.
LOG_NEWS
The network news system.
LOG_SYSLOG
Messages generated internally by syslogd(8).
LOG_USER
Messages generated by random user processes. This
is the default facility identifier if none is spec-
ified.
LOG_UUCP
The uucp system.
LOG_LOCAL0
Reserved for local use. Similarly for LOG_LOCAL1
through LOG_LOCAL7.
Closelog can be used to close the log file.
Setlogmask sets the log priority mask to maskpri and
returns the previous mask. Calls to syslog with a prior-
ity not set in maskpri are rejected. The mask for an
individual priority pri is calculated by the macro
LOG_MASK(pri); the mask for all priorities up to and
including toppri is given by the macro LOG_UPTO(toppri).
The default allows all priorities to be logged.
EXAMPLES
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");
SEE ALSOlogger(1), syslogd(8)
June 23, 1990 SYSLOG(3)
