fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
296 lines
7.3 KiB
Groff
296 lines
7.3 KiB
Groff
.\" Copyright (c) 1985, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)syslog.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd July 21, 2015
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.Dt SYSLOG 3
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.Os
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.Sh NAME
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.Nm syslog ,
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.Nm vsyslog ,
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.Nm openlog ,
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.Nm closelog ,
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.Nm setlogmask
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.Nd control system log
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In syslog.h
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.In stdarg.h
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.Ft void
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.Fn syslog "int priority" "const char *message" "..."
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.Ft void
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.Fn vsyslog "int priority" "const char *message" "va_list args"
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.Ft void
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.Fn openlog "const char *ident" "int logopt" "int facility"
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.Ft void
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.Fn closelog void
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.Ft int
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.Fn setlogmask "int maskpri"
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.Sh DESCRIPTION
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The
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.Fn syslog
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function
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writes
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.Fa message
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to the system message logger.
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The message is then written to the system console, log files,
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logged-in users, or forwarded to other machines as appropriate.
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(See
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.Xr syslogd 8 . )
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.Pp
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The message is identical to a
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.Xr printf 3
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format string, except that
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.Ql %m
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is replaced by the current error
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message.
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(As denoted by the global variable
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.Va errno ;
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see
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.Xr strerror 3 . )
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A trailing newline is added if none is present.
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.Pp
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The
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.Fn vsyslog
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function
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is an alternate form in which the arguments have already been captured
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using the variable-length argument facilities of
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.Xr stdarg 3 .
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.Pp
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The message is tagged with
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.Fa priority .
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Priorities are encoded as a
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.Fa facility
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and a
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.Em level .
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The facility describes the part of the system
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generating the message.
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The level is selected from the following
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.Em ordered
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(high to low) list:
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.Bl -tag -width LOG_AUTHPRIV
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.It Dv LOG_EMERG
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A panic condition.
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This is normally broadcast to all users.
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.It Dv LOG_ALERT
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A condition that should be corrected immediately, such as a corrupted
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system database.
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.It Dv LOG_CRIT
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Critical conditions, e.g., hard device errors.
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.It Dv LOG_ERR
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Errors.
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.It Dv LOG_WARNING
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Warning messages.
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.It Dv LOG_NOTICE
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Conditions that are not error conditions,
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but should possibly be handled specially.
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.It Dv LOG_INFO
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Informational messages.
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.It Dv LOG_DEBUG
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Messages that contain information
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normally of use only when debugging a program.
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.El
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.Pp
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The
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.Fn openlog
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function
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provides for more specialized processing of the messages sent
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by
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.Fn syslog
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and
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.Fn vsyslog .
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The
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.Fa ident
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argument
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is a string that will be prepended to every message.
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The
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.Fa logopt
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argument
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is a bit field specifying logging options, which is formed by
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.Tn OR Ns 'ing
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one or more of the following values:
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.Bl -tag -width LOG_AUTHPRIV
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.It Dv LOG_CONS
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If
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.Fn syslog
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cannot pass the message to
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.Xr syslogd 8
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it will attempt to write the message to the console
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.Pq Dq Pa /dev/console .
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.It Dv LOG_NDELAY
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Open the connection to
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.Xr syslogd 8
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immediately.
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Normally the open is delayed until the first message is logged.
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Useful for programs that need to manage the order in which file
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descriptors are allocated.
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.It Dv LOG_PERROR
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Write the message to standard error output as well to the system log.
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.It Dv LOG_PID
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Log the process id with each message: useful for identifying
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instantiations of daemons.
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.El
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.Pp
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The
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.Fa facility
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argument encodes a default facility to be assigned to all messages
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that do not have an explicit facility encoded:
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.Bl -tag -width LOG_AUTHPRIV
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.It Dv LOG_AUTH
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The authorization system:
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.Xr login 1 ,
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.Xr su 1 ,
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.Xr getty 8 ,
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etc.
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.It Dv LOG_AUTHPRIV
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The same as
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.Dv LOG_AUTH ,
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but logged to a file readable only by
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selected individuals.
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.It Dv LOG_CONSOLE
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Messages written to
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.Pa /dev/console
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by the kernel console output driver.
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.It Dv LOG_CRON
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The cron daemon:
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.Xr cron 8 .
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.It Dv LOG_DAEMON
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System daemons, such as
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.Xr routed 8 ,
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that are not provided for explicitly by other facilities.
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.It Dv LOG_FTP
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The file transfer protocol daemons:
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.Xr ftpd 8 ,
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.Xr tftpd 8 .
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.It Dv LOG_KERN
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Messages generated by the kernel.
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These cannot be generated by any user processes.
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.It Dv LOG_LPR
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The line printer spooling system:
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.Xr lpr 1 ,
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.Xr lpc 8 ,
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.Xr lpd 8 ,
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etc.
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.It Dv LOG_MAIL
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The mail system.
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.It Dv LOG_NEWS
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The network news system.
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.It Dv LOG_NTP
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The network time protocol system.
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.It Dv LOG_SECURITY
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Security subsystems, such as
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.Xr ipfw 4 .
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.It Dv LOG_SYSLOG
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Messages generated internally by
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.Xr syslogd 8 .
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.It Dv LOG_USER
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Messages generated by random user processes.
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This is the default facility identifier if none is specified.
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.It Dv LOG_UUCP
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The uucp system.
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.It Dv LOG_LOCAL0
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Reserved for local use.
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Similarly for
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.Dv LOG_LOCAL1
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through
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.Dv LOG_LOCAL7 .
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.El
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.Pp
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The
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.Fn closelog
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function
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can be used to close the log file.
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.Pp
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The
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.Fn setlogmask
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function
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sets the log priority mask to
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.Fa maskpri
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and returns the previous mask.
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Calls to
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.Fn syslog
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with a priority not set in
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.Fa maskpri
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are rejected.
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The mask for an individual priority
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.Fa pri
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is calculated by the macro
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.Fn LOG_MASK pri ;
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the mask for all priorities up to and including
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.Fa toppri
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is given by the macro
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.Fn LOG_UPTO toppri ; .
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The default allows all priorities to be logged.
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.Sh RETURN VALUES
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The routines
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.Fn closelog ,
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.Fn openlog ,
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.Fn syslog
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and
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.Fn vsyslog
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return no value.
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.Pp
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The routine
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.Fn setlogmask
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always returns the previous log mask level.
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.Sh EXAMPLES
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.Bd -literal -offset indent -compact
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syslog(LOG_ALERT, "who: internal error 23");
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openlog("ftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
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setlogmask(LOG_UPTO(LOG_ERR));
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syslog(LOG_INFO, "Connection from host %d", CallingHost);
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syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");
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.Ed
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.Sh SEE ALSO
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.Xr logger 1 ,
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.Xr syslogd 8
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.Sh HISTORY
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These
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functions appeared in
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.Bx 4.2 .
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.Sh BUGS
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Never pass a string with user-supplied data as a format without using
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.Ql %s .
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An attacker can put format specifiers in the string to mangle your stack,
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leading to a possible security hole.
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This holds true even if the string was built using a function like
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.Fn snprintf ,
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as the resulting string may still contain user-supplied conversion specifiers
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for later interpolation by
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.Fn syslog .
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.Pp
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Always use the proper secure idiom:
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.Pp
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.Dl syslog(priority, "%s", string);
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