syslog(3) C LIBRARY FUNCTIONS syslog(3)
NAME
syslog, openlog, closelog, setlogmask - control system log
SYNOPSIS
cc [ flag... ] file ... -lucb
#include <syslog.h>
openlog(ident, logopt, facility)
char *ident;
syslog(priority, message, parameters ... )
char *message;
closelog()
setlogmask(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 sys-
logd on another host over the network. The message is
tagged with a priority of priority. The message looks like
a printf(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:
LOGEMERG A panic condition. This is nor-
mally broadcast to all users.
LOGALERT A condition that should be
corrected immediately, such as a
corrupted system database.
LOGCRIT Critical conditions, such as hard
device errors.
LOGERR Errors.
LOGWARNING Warning messages.
LOGNOTICE Conditions that are not error con-
ditions, but that may require spe-
cial handling.
LOGINFO Informational messages.
LOGDEBUG 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
Last change: BSD Compatibility Package 1
syslog(3) C LIBRARY FUNCTIONS syslog(3)
indicating logging options. Current values for logopt are:
LOGPID Log the process ID with each mes-
sage. This is useful for identify-
ing specific daemon processes (for
daemons that fork).
LOGCONS Write messages to the system con-
sole if they cannot be sent to sys-
logd. This option is safe to use
in daemon processes that have no
controlling terminal, since syslog
forks before opening the console.
LOGNDELAY Open the connection to syslogd
immediately. Normally the open is
delayed until the first message is
logged. This is useful for pro-
grams that need to manage the order
in which file descriptors are allo-
cated.
LOGNOWAIT Do not wait for child processes
that have been forked to log mes-
sages 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 facil-
ity already encoded:
LOGKERN Messages generated by the kernel.
These cannot be generated by any
user processes.
LOGUSER Messages generated by random user
processes. This is the default
facility identifier if none is
specified.
LOGMAIL The mail system.
LOGDAEMON System daemons, such as ftpd(1M),
routed(1M), etc.
LOGAUTH The authorization system:
login(1), su(1), getty(1M), etc.
Last change: BSD Compatibility Package 2
syslog(3) C LIBRARY FUNCTIONS syslog(3)
LOGLPR The line printer spooling system:
lpr(1), lpc(1M), etc.
LOGNEWS Reserved for the USENET network
news system.
LOGUUCP Reserved for the UUCP system; it
does not currently use syslog.
LOGCRON The cron/at facility; crontab(1),
at(1), cron(1M), etc.
LOGLOCAL0-7 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 LOGMASK(pri); the mask for all
priorities up to and including toppri is given by the macro
LOGUPTO(toppri). The default allows all priorities to be
logged.
EXAMPLE
This call logs a message at priority LOGALERT:
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 identify-
ing 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);
Then it would make the following call to setlogmask to indi-
cate that messages at priorities from LOGEMERG through
LOGERR should be logged, but that no messages at any other
priority should be logged:
setlogmask(LOGUPTO(LOG_ERR));
Then, to log a message at priority LOGINFO, it would make
the following call to syslog:
syslog(LOGINFO, "Connection from host %d", Cal-
lingHost);
A locally-written utility could use the following call to
syslog to log a message at priority LOGINFO, to be treated
by syslogd as other messages to the facility LOGLOCAL2 are
treated:
syslog(LOGINFO|LOGLOCAL2, "error: %m");
SEE ALSO
logger(1), login(1), lpr(1), lpc(1M), syslogd(1M),
printf(3S) at(1), crontab(1), login(1) in the User's Refer-
ence Manual.
ftpd(1M), routed(1M) in the Network User's and
Administrator's Guide.
Last change: BSD Compatibility Package 3
syslog(3) C LIBRARY FUNCTIONS syslog(3)
getty(1M), cron(1M), su(1), printf(3S) in the System
Administrator's Reference Manual.
Last change: BSD Compatibility Package 4