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.\" @(#)logger.1 8.1 (Berkeley) 6/6/93
.\"
.TH LOGGER "1" "March 2015" "util-linux" "User Commands"
.SH NAME
logger \- enter messages into the system log
.SH SYNOPSIS
.B logger
[options]
.RI [ message ]
.SH DESCRIPTION
.B logger
makes entries in the system log.
.sp
When the optional \fImessage\fR argument is present, it is written
to the log. If it is not present, and the \fB\-f\fR option is not
given either, then standard input is logged.
.SH OPTIONS
.TP
.BR \-d , " \-\-udp"
Use datagrams (UDP) only. By default the connection is tried to the
syslog port defined in /etc/services, which is often 514 .
.TP
.BR \-e , " \-\-skip-empty"
When processing files, empty lines will be ignored. An empty line
is defined to be a line without any characters. Thus a line consisting
only of whitespace is NOT considered empty.
Note that when the \fR\-\-prio\-prefix\fR option is specified, the priority
is not part of the line. Thus an empty line in this mode is a line that does
not have any characters after the priority (e.g. "<13>").
.TP
.BR \-f , " \-\-file " \fIfile
Log the contents of the specified \fIfile\fR.
This option cannot be combined with a command-line message.
.TP
.B \-i
Log the PID of the logger process with each line.
.TP
.BR "\-\-id" [ =\fIid ]
Log the PID of the logger process with each line. When the optional
argument \fIid\fR is specified, then it is used instead of the logger
command's PID. The use of \fB\-\-id=$$\fR
(PPID) is recommended in scripts that send several messages.
.TP
.BR \-\-journald [ =\fIfile ]
Write a systemd journal entry. The entry is read from the given \fIfile\fR,
when specified, otherwise from standard input.
Each line must begin with a field that is accepted by journald; see
.BR systemd.journal-fields (7)
for details. The use of a MESSAGE_ID field is generally a good idea, as it
makes finding entries easy. Examples:
.IP
.nf
\fB printf \(dq%s\\n%s\\n%s\\n\(dq MESSAGE_ID=42 DOGS=bark \(dqCARAVAN=goes on\(dq | logger --journald
\fB logger --journald=entry.txt
.fi
.IP
Notice that
.B \-\-journald
will ignore values of other options, such as priority. If priority is
needed it must be within input, and use PRIORITY field. The simple
execution of
.B journalctl
will display MESSAGE field. Use
.B journalctl --output json-pretty
to see rest of the fields.
.TP
.BR \-\--size " \fIsize
Sets the maximum permitted message size to \fIsize\fR. The default
is 1KiB characters, which is the limit traditionally used and specified
in RFC 3164. With RFC 5424, this limit has become flexible. A good assumption
is that RFC 5424 receivers can at least process 4KiB messages.
Most receivers accept larger than 1KiB message over any type of syslog
protocol. As such, the \fB\-\-size\fR option affects logger in
all cases (not only when \fB\-\-rfc5424\fR was used).
Note: the message size limit limits the overall message size, including
the syslog header. Header sizes vary depending on options selected and hostname
length. As a rule of thumb, headers are usually not longer than 50 to 80
characters. When selecting maximum message size, it is important to ensure
that the receiver supports the max size as well, otherwise messages may
become truncated. Again, as a rule of thumb two to four KiB message size
should generally be OK, whereas anything larger should be verified to work.
.TP
.BR \-n , " \-\-server " \fIserver
Write to the specified remote syslog \fIserver\fR
instead of to the system log socket. Unless
\fB\-\-udp\fR or \fB\-\-tcp\fR
is specified, \fBlogger\fR will first try to use UDP,
but if thist fails a TCP connection is attempted.
.TP
.BR \-P , " \-\-port " \fIport
Use the specified \fIport\fR. When this option is not specified, the
port defaults to syslog for udp and to syslog-conn for tcp connections.
.TP
.BR \-p , " \-\-priority " \fIpriority
Enter the message into the log with the specified \fIpriority\fR.
The priority may be specified numerically or as a
.IR facility . level
pair.
For example, \fB\-p local3.info\fR
logs the message as informational in the local3 facility.
The default is \fBuser.notice\fR.
.TP
.B \-\-prio\-prefix
Look for a syslog prefix on every line read from standard input.
This prefix is a decimal number within angle brackets that encodes both
the facility and the level. The number is constructed by multiplying the
facility by 8 and then adding the level. For example, \fBlocal0.info\fR,
meaning facility=16 and level=6, becomes \fB<134>\fR.
.sp
If the prefix contains no facility, the facility defaults to what is
specified by the \fB\-p\fR option. Similarly, if no prefix is provided,
the line is logged using the \fIpriority\fR given with \fB\-p\fR.
.sp
This option doesn't affect a command-line message.
.TP
.B \-\-rfc3164
Use the RFC 3164 BSD syslog protocol to submit messages to a remote server.
.TP
.BR \-\-rfc5424 [ =\fIwithout ]
Use the RFC 5424 syslog protocol to submit messages to a remote server.
The optional \fIwithout\fR argument can be a comma-separated list of
the following values: \fBnotq\fR, \fBnotime\fR, \fBnohost\fR.
The \fBnotq\fR value suppresses the time-quality structured data
from the submitted message. (The time-quality information shows whether
the local clock was synchronized plus the maximum number of microseconds
the timestamp might be off.) The \fBnotime\fR value (which implies
\fBnotq\fR) suppresses the complete sender timestamp that is in
ISO-8601 format, including microseconds and timezone.
The \fBnohost\fR value suppresses
.BR gethostname (2)
information from the message header.
.IP
The RFC 5424 protocol has been the default for
.B logger
since version 2.26.
.TP
.BR \-s , " \-\-stderr"
Output the message to standard error as well as to the system log.
.TP
.BR \-T , " \-\-tcp"
Use stream (TCP) only. By default the connection is tried to the
.I syslog-conn
port defined in /etc/services, which is often
.IR 601 .
.TP
.BR \-t , " \-\-tag " \fItag
Mark every line to be logged with the specified
.IR tag .
.TP
.BR \-u , " \-\-socket " \fIsocket
Write to the specified
.I socket
instead of to the system log socket.
.TP
.BR \-\-socket\-errors [ =\fImode ]
Print errors about Unix socket connections. The \fImode\fR can be a value of
\fBoff\fR, \fBon\fR, or \fBauto\fR. When the mode is auto logger will detect
if the init process is systemd, and if so assumption is made /dev/log can be
used early at boot. Other init systems lack of /dev/log will not cause errors
that is identical with messaging using
.BR openlog (3)
system call. The
.BR logger (1)
before version 2.26 used openlog, and hence was inable to detected loss of
messages sent to Unix sockets.
.IP
The default mode is \fBauto\fR. When errors are not enabled lost messages are
not communicated and will result to successful return value of
.BR logger (1)
invocation.
.TP
.B \-\-
End the argument list. This allows the \fImessage\fR
to start with a hyphen (\-).
.TP
.BR \-V , " \-\-version"
Display version information and exit.
.TP
.BR \-h , " \-\-help"
Display help text and exit.
.SH RETURN VALUE
The
.B logger
utility exits 0 on success, and >0 if an error occurs.
.SH FACILITIES AND LEVELS
Valid facility names are:
.IP
.TS
tab(:);
left l l.
\fBauth
\fBauthpriv\fR:for security information of a sensitive nature
\fBcron
\fBdaemon
\fBftp
\fBkern\fR:cannot be generated from user process
\fBlpr
\fBmail
\fBnews
\fBsyslog
\fBuser
\fBuucp
\fBlocal0
to:
\fBlocal7
\fBsecurity\fR:deprecated synonym for \fBauth
.TE
.PP
Valid level names are:
.IP
.TS
tab(:);
left l l.
\fBemerg
\fBalert
\fBcrit
\fBerr
\fBwarning
\fBnotice
\fBinfo
\fBdebug
\fBpanic\fR:deprecated synonym for \fBemerg
\fBerror\fR:deprecated synonym for \fBerr
\fBwarn\fR:deprecated synonym for \fBwarning
.TE
.PP
For the priority order and intended purposes of these facilities and levels, see
.BR syslog (3).
.SH EXAMPLES
.B logger System rebooted
.br
.B logger \-p local0.notice \-t HOSTIDM \-f /dev/idmc
.br
.B logger \-n loghost.example.com System rebooted
.SH SEE ALSO
.BR syslog (3),
.BR journalctl (1),
.BR systemd.journal-fields (7)
.SH STANDARDS
The
.B logger
command is expected to be IEEE Std 1003.2 ("POSIX.2") compatible.
.SH AVAILABILITY
The logger command is part of the util-linux package and is available from
.UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
Linux Kernel Archive
.UE .