Manual page for SYSLOG(3)
syslog, openlog, closelog, setlogmask - control system log
SYNOPSIS
#include <syslog.h>
openlog(ident, logopt, facility)
char *ident;
syslog(priority, message, parameters ... )
char *message;
closelog()
setlogmask(maskpri)
DESCRIPTION
Syslog
arranges to write
message
onto the system log maintained by
syslogd.8
The message is tagged with
priority.
The message looks like a
printf.3
string except that
%m
is replaced by the current error message (collected from
errno).
A trailing newline is added if needed.
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_EMERG
-
A panic condition.
This is normally broadcast to all users.
- 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_ERR
-
Errors.
- LOG_WARNING
-
Warning messages.
- LOG_NOTICE
-
Conditions that are not error conditions,
but should possibly be handled specially.
- LOG_INFO
-
Informational messages.
- LOG_DEBUG
-
Messages that contain information
normally of use only when debugging a program.
If
syslog
cannot pass the message to
syslogd,
it will attempt to write the message on
/dev/console
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_PID
-
log the process id with each message:
useful for identifying instantiations of daemons.
- LOG_CONS
-
Force writing messages to the console if unable to send it to
syslogd.
This option is safe to use in daemon processes that have no controlling
terminal since
syslog
will fork before opening the console.
- LOG_NDELAY
-
Open the connection to
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.
- LOG_NOWAIT
-
Don't wait for children forked to log messages on the console.
This option should be used by processes that enable notification
of child termination via SIGCHLD, as
syslog
may otherwise block waiting for a child whose exit status has already
been collected.
The
facility
parameter encodes a default facility to be assigned to all messages
that do not have an explicit facility encoded:
- LOG_KERN
-
Messages generated by the kernel.
These cannot be generated by any user processes.
- LOG_USER
-
Messages generated by random user processes.
This is the default facility identifier if none is specified.
- LOG_MAIL
-
The mail system.
- LOG_DAEMON
-
System daemons, such as
ftpd.8
routed.8
etc.
- LOG_AUTH
-
The authorization system:
login.1
su.1
getty.8
etc.
- LOG_LPR
-
The line printer spooling system:
lpr.1
lpc.8
lpd.8
etc.
- 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 priority 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 ALSO
logger(1),
syslogd(8)
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97
