SYSLOG

Section: C Library Functions (3)
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BSD mandoc
BSD 4.2

NAME

syslog vsyslog openlog closelog setlogmask - control system log

SYNOPSIS

Fd #include <syslog.h> Fd #include <varargs.h> Ft void Fn syslog int priority const char *message ... Ft void Fn vsyslog int priority const char *message va_list args Ft void Fn openlog const char *ident int logopt int facility Ft void Fn closelog void Ft int Fn setlogmask int maskpri

DESCRIPTION

The Fn syslog function writes Fa 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 variable errno see strerror(3).) A trailing newline is added if none is present.

The Fn 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 Fa priority . Priorities are encoded as a Fa 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 possibly be handled specially.
LOG_INFO: Informational messages.
LOG_DEBUG: Messages that contain information normally of use only when debugging a program.

The Fn openlog function provides for more specialized processing of the messages sent by Fn syslog and Fn vsyslog . The parameter Fa ident is a string that will be prepended to every message. The Fa 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 Fn syslog cannot pass the message to syslogd it will attempt 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 identifying instantiations of daemons.

The Fa 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 cron daemon: cron(8).
LOG_DAEMON: System daemons, such as routed(8), that are not provided for explicitly by other facilities.
LOG_FTP: The file transfer protocol daemon: ftpd(8).
LOG_KERN: Messages generated by the kernel. These cannot be generated 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 Fn closelog function can be used to close the log file.

The Fn setlogmask function sets the log priority mask to Fa maskpri and returns the previous mask. Calls to Fn syslog with a priority not set in Fa maskpri are rejected. The mask for an individual priority Fa pri is calculated by the macro Fn LOG_MASK pri ; the mask for all priorities up to and including Fa toppri is given by the macro Fn LOG_UPTO toppri ; . The default allows all priorities to be logged.

RETURN VALUES

The routines Fn closelog , Fn openlog , Fn syslog and Fn vsyslog return no value.

The routine Fn setlogmask always returns the previous log mask level.

EXAMPLES

syslog(LOG_ALERT, "who: internal error 23");

openlog("ftpd", LOG_PID | LOG_NDELAY, LOG_FTP);

setlogmask(LOG_UPTO(LOG_ERR));

syslog(LOG_INFO, "Connection from host %d", CallingHost);

syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");

HISTORY

These functions appeared in BSD 4.2

This document was created by man2html, using the manual pages.
Time: 19:42:02 GMT, December 25, 2022