SYSLOG(3) MachTen Programmer’s Manual SYSLOG(3)

NAME
syslog, vsyslog, openlog, closelog, setlogmask - control system log

SYNOPSIS
#include <syslog.h>
#include <varargs.h>

void
syslog(int priority, const char *message, ...)

void
vsyslog(int priority, const char *message, va_list args)

void
openlog(const char *ident, int logopt, int facility)

void
closelog(void)

int
setlogmask(int maskpri)

DESCRIPTION
The syslog() function writes message to the system message logger. The
message is then written to the system console, log files, logged-in
users, or forwarded to other machines as appropriate. (See syslogd(8).)

The message is identical to a printf(3) format string, except that ‘%m’
is replaced by the current error message. (As denoted by the global vari-
able errno; see strerror(3).) A trailing newline is added if none is
present.

The vsyslog() function is an alternate form in which the arguments have
already been captured using the variable-length argument facilities of
varargs(3).

The message is tagged with priority. 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 the following ordered (high to low)
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 possi-
bly be handled specially.

LOG_INFO Informational messages.

LOG_DEBUG Messages that contain information normally of use only when
debugging a program.

The openlog() function provides for more specialized processing of the
messages sent by syslog() and vsyslog(). The parameter ident is a string
that will be prepended to every message. The logopt argument is a bit
field specifying logging options, which is formed by OR’ing one or more
of the following values:

LOG_CONS If syslog() cannot pass the message to syslogd it will at-
tempt to write the message to the console
(‘‘/dev/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_PERROR Write the message to standard error output as well to the
system log.

LOG_PID Log the process id with each message: useful for identify-
ing 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_AUTHPRIV The same as LOG_AUTH, but logged to a file readable only by
selected individuals.

LOG_CRON The clock daemon.

LOG_DAEMON System daemons, such as routed(8), that are not provided
for explicitly by other facilities.

LOG_KERN Messages generated by the kernel. These cannot be generat-
ed 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 specified.

LOG_UUCP The uucp system.

LOG_LOCAL0 Reserved for local use. Similarly for LOG_LOCAL1 through
LOG_LOCAL7.

The closelog() function can be used to close the log file.

The setlogmask() function sets the log priority mask to maskpri and re-
turns the previous mask. Calls to syslog() with a priority not set in
maskpri are rejected. The mask for an individual priority pri is calcu-
lated 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 al-
lows all priorities to be logged.

RETURN VALUES
The routines closelog(), openlog(), syslog() and vsyslog() return no val-
ue.

The routine setlogmask() always returns the previous log mask level.

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");