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()
passes
message
to
syslogd.8
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.3v
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.
- 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_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.
- LOG_MAIL
-
The mail system.
- LOG_DAEMON
-
System daemons, such as
ftpd.8c
routed.8c
etc.
- LOG_AUTH
-
The authorization system:
login.1
su.1v
getty.8
etc.
- LOG_LPR
-
The line printer spooling system:
lpr.1
lpc.8
lpd.8
etc.
- LOG_NEWS
-
Reserved for the
USENET
network news system.
- LOG_UUCP
-
Reserved for the
UUCP
system; it does not currently use
syslog.
- LOG_CRON
-
The
cron/at
facility;
crontab.1
at.1
cron.8
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.
EXAMPLES
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,
should include the process
ID
of the process logging the message:
-
openlog("ftpd", LOG_PID, LOG_DAEMON);
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:
-
syslog(LOG_INFO|LOG_LOCAL2, "error: %m");
SEE ALSO
at.1
crontab.1
logger.1
login.1
lpr.1
su.1v
printf.3v
syslog.conf.5
cron.8
ftpd.8c
getty.8
lpc.8
lpd.8
routed.8c
syslogd.8
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97