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28 .\" @(#)syslog.3 8.1 (Berkeley) 6/4/93
29 .\" $FreeBSD: src/lib/libc/gen/syslog.3,v 1.9.2.9 2001/12/14 18:33:51 ru Exp $
30 .\" $DragonFly: src/lib/libc/gen/syslog.3,v 1.2 2003/06/17 04:26:42 dillon Exp $
41 .Nd control system log
48 .Fn syslog "int priority" "const char *message" "..."
50 .Fn vsyslog "int priority" "const char *message" "va_list args"
52 .Fn openlog "const char *ident" "int logopt" "int facility"
56 .Fn setlogmask "int maskpri"
63 to the system message logger.
64 The message is then written to the system console, log files,
65 logged-in users, or forwarded to other machines as appropriate.
69 The message is identical to a
71 format string, except that
73 is replaced by the current error
75 (As denoted by the global variable
79 A trailing newline is added if none is present.
84 is an alternate form in which the arguments have already been captured
85 using the variable-length argument facilities of
88 The message is tagged with
90 Priorities are encoded as a
94 The facility describes the part of the system
95 generating the message.
96 The level is selected from the following
99 .Bl -tag -width LOG_AUTHPRIV
102 This is normally broadcast to all users.
104 A condition that should be corrected immediately, such as a corrupted
107 Critical conditions, e.g., hard device errors.
113 Conditions that are not error conditions,
114 but should possibly be handled specially.
116 Informational messages.
118 Messages that contain information
119 normally of use only when debugging a program.
125 provides for more specialized processing of the messages sent
132 is a string that will be prepended to every message.
136 is a bit field specifying logging options, which is formed by
138 one or more of the following values:
139 .Bl -tag -width LOG_AUTHPRIV
143 cannot pass the message to
145 it will attempt to write the message to the console
146 .Pq Dq Pa /dev/console .
148 Open the connection to
151 Normally the open is delayed until the first message is logged.
152 Useful for programs that need to manage the order in which file
153 descriptors are allocated.
155 Write the message to standard error output as well to the system log.
157 Log the process id with each message: useful for identifying
158 instantiations of daemons.
163 parameter encodes a default facility to be assigned to all messages
164 that do not have an explicit facility encoded:
165 .Bl -tag -width LOG_AUTHPRIV
167 The authorization system:
175 but logged to a file readable only by
176 selected individuals.
180 by the kernel console output driver.
185 System daemons, such as
187 that are not provided for explicitly by other facilities.
189 The file transfer protocol daemons:
193 Messages generated by the kernel.
194 These cannot be generated by any user processes.
196 The line printer spooling system:
204 The network news system.
206 Security subsystems, such as
209 Messages generated internally by
212 Messages generated by random user processes.
213 This is the default facility identifier if none is specified.
217 Reserved for local use.
227 can be used to close the log file.
232 sets the log priority mask to
234 and returns the previous mask.
237 with a priority not set in
240 The mask for an individual priority
242 is calculated by the macro
244 the mask for all priorities up to and including
246 is given by the macro
247 .Fn LOG_UPTO toppri ; .
248 The default allows all priorities to be logged.
260 always returns the previous log mask level.
262 .Bd -literal -offset indent -compact
263 syslog(LOG_ALERT, "who: internal error 23");
265 openlog("ftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
267 setlogmask(LOG_UPTO(LOG_ERR));
269 syslog(LOG_INFO, "Connection from host %d", CallingHost);
271 syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");
278 functions appeared in