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syslog(SLIB)


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

Syntax

cc ... -lsocket

#include  <syslog.h>

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

void syslog(priority, message [, arg ] . . . int priority; const char *message;

void closelog()

int setlogmask(maskpri) /* Returns old mask */ int maskpri;

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

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

Description

syslog arranges to write message onto the system log maintained by syslogd(ADM). message is tagged with priority. message is processed like the format parameter to printf(S), except that the additional conversion specifier %m can be used; it is replaced with the current error message in errno. A trailing newline is added to message if one is not supplied. The behavior of syslog is undefined if there are more conversion specifiers in message than matching args. If there are more args than conversion specifiers, the extra args are ignored.

vsyslog works just like syslog, except that the arguments used to replace any conversion specifiers in message have already been captured using the variable-length argument facilities of varargs(S).

message is read by syslogd and written either to the system console, log files, or forwarded to syslogd on another host.

Priorities are encoded as a facility and a level. facility describes the part of the system generating the message. 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, for example, hard device errors.

LOG_ERR
Errors.

LOG_WARNING
Warning messages.

LOG_NOTICE
Conditions that are not error conditions, but may require special handling.

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 attempts to write the message on /dev/console (if the LOG_CONS option is set).

If special processing is needed, openlog can be called to initialize the log file. ident is a string that is prepended to every message. logopt is a bit field indicating logging options. Possible values for logopt are:


LOG_PID
Log the process id with each message. This is 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 because 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 forked children to log messages on the console. This option should be used by processes that enable notification of child termination via SIGCHLD, because syslog may otherwise block waiting for a child whose exit status has already been collected.

LOG_PERROR
Write the message to stderr.

facility encodes a default facility to be assigned to all messages that do not have an explicit facility encoded:


LOG_AUTH
Messages generated by programs that authenticate users.

LOG_AUTHPRIV
Messages generated by programs that authenticate users.

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(ADMN), routed(ADMN), etc.

LOG_NEWS
The network news system.

LOG_SYSLOG
Messages generated internally by syslogd.

LOG_UUCP
Messages generated by programs that deal with uucp(C).

LOG_LPR
The line printer spooling system lpd(ADMN).

LOG_LOCAL0
Reserved for local use. LOG_LOCAL1 through LOG_LOCAL7 are also reserved.

closelog closes 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

   openlog("ftpd", LOG_PID, LOG_DAEMON);
   setlogmask(LOG_UPTO(LOG_ERR));
   syslog(LOG_ALERT, "who: internal error 23");
   syslog(LOG_INFO, "Connection from host %d", callinghostname);
   syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");
   syslog(LOG_INFO, "This is the %d connection from host %s",
          connection_id, callinghostname);
   syslog(LOG_INFO,
          "Connection number %d from host %s failed with error: %m",
          connection_id, callinghostname);

See also

logger(C), syslogd(ADM)


© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003