syslog(3G) syslog(3G)
NAME
syslog, openlog, closelog, setlogmask - control system log
SYNOPSIS
cc [flag . . . ] file . . . -lgen [library] . . .
#include <syslog.h>
void openlog(const char *ident, int logopt, int facility);
void syslog(int priority, const char *message, . . . /* parameters */);
void closelog();
int setlogmask(int maskpri);
DESCRIPTION
syslog passes message to syslogd(1M), which logs it in an
appropriate system log, writes it to the system console,
forwards it to a list of users, or forwards it to the syslogd
on another host over the network. The message is tagged with
a priority of priority. The message looks like a printf [see
fprintf(3S)] string except that %m is replaced by the current
error message (collected from errno). A trailing NEWLINE is
added if needed.
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, such as hard device
errors.
LOG_ERR Errors.
LOG_WARNING Warning messages.
LOG_NOTICE Conditions that are not error conditions,
but that may require special handling.
LOG_INFO Informational messages.
Copyright 1994 Novell, Inc. Page 1
syslog(3G) syslog(3G)
LOG_DEBUG Messages that contain information normally
of use only when debugging a program.
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.
This is useful for identifying specific
daemon processes (for daemons that fork).
LOG_CONS Write messages to the system console if
they cannot be sent to syslogd. This
option is safe to use in daemon processes
that have no controlling terminal, since
syslog forks before opening the console.
LOG_NDELAY Open the connection to syslogd
immediately. Normally the open is delayed
until the first message is logged. This
is useful for programs that need to manage
the order in which file descriptors are
allocated.
LOG_ODELAY Delay open until syslog() is called.
LOG_NOWAIT Do not wait for child processes that have
been forked to log messages onto the
console. This option should be used by
processes that enable notification of
child termination using SIGCHLD, since
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
already 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.
Copyright 1994 Novell, Inc. Page 2
syslog(3G) syslog(3G)
LOG_MAIL The mail system.
LOG_DAEMON System daemons, such as ftpd(1M),
routed(1M), etc.
LOG_AUTH The authorization system: login(1),
su(1M), getty(1M), etc.
LOG_SYSLOG Messages generated internally by syslogd.
LOG_LPR The line printer spooling system:
lpr(1BSD), lpc(1M_BSD), etc.
LOG_NEWS Reserved for the USENET network news
system.
LOG_UUCP Reserved for the UUCP system; it does not
currently use syslog.
LOG_LFMT The log alert facility.
LOG_CRON The cron/at facility; crontab(1), at(1),
cron(1M), etc.
LOG_LOCAL0-7 Reserved for local use.
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.
EXAMPLE
This call logs a message at priority LOG_ALERT:
syslog(LOG_ALERT, "who: internal error 23");
The FTP daemon, ftpd, would make this call to openlog to
indicate that all messages it logs should have an identifying
string of ftpd, should be treated by syslogd as other messages
from system daemons are, and should include the process ID of
the process logging the message:
openlog("ftpd", LOG_PID, LOG_DAEMON);
Copyright 1994 Novell, Inc. Page 3
syslog(3G) syslog(3G)
Then it would make the following call to setlogmask to
indicate that messages at priorities from LOG_EMERG through
LOG_ERR should be logged, but that no messages at any other
priority should be logged:
setlogmask(LOG_UPTO(LOG_ERR));
Then, to log a message at priority LOG_INFO, it would make the
following call to syslog:
syslog(LOG_INFO, "Connection from host %d", CallingHost);
A locally-written utility could use the following call to
syslog to log a message at priority LOG_INFO, to be treated by
syslogd as other messages to the facility LOG_LOCAL2 are
treated:
syslog(LOG_INFO|LOG_LOCAL2, "error: %m");
REFERENCES
at(1), cron(1M), crontab(1), fprintf(3S), ftpd(1M), getty(1M),
logger(1BSD), login(1), lpc(1M_BSD), lpr(1BSD), routed(1M),
su(1M), syslogd(1M)
Copyright 1994 Novell, Inc. Page 4