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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | FACILITIES AND LEVELS | CONFORMING TO | EXAMPLES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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LOGGER(1) User Commands LOGGER(1)
logger - enter messages into the system log
logger [options] message
logger makes entries in the system log.
When the optional message argument is present, it is written to
the log. If it is not present, and the -f option is not given
either, then standard input is logged.
-d, --udp
Use datagrams (UDP) only. By default the connection is tried
to the syslog port defined in /etc/services, which is often
514.
See also --server and --socket to specify where to connect.
-e, --skip-empty
Ignore empty lines when processing files. 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 --prio-prefix 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
prefix (e.g., <13>).
-f, --file file
Log the contents of the specified file. This option cannot be
combined with a command-line message.
-i
Log the PID of the logger process with each line.
--id[=id]
Log the PID of the logger process with each line. When the
optional argument id is specified, then it is used instead of
the logger command’s PID. The use of --id=$$ (PPID) is
recommended in scripts that send several messages.
Note that the system logging infrastructure (for example
systemd when listening on /dev/log) may follow local socket
credentials to override the PID specified in the message.
logger(1) is able to set those socket credentials to the given
id, but only if you have root permissions and a process with
the specified PID exists, otherwise the socket credentials are
not modified and the problem is silently ignored.
--journald[=file]
Write a systemd journal entry. The entry is read from the
given file, when specified, otherwise from standard input.
Each line must begin with a field that is accepted by
journald; see 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:
logger --journald <<end
MESSAGE_ID=67feb6ffbaf24c5cbec13c008dd72309
MESSAGE=The dogs bark, but the caravan goes on.
DOGS=bark
CARAVAN=goes on
end
logger --journald=entry.txt
Notice that --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
journalctl(1) will display MESSAGE field. Use journalctl
--output json-pretty to see rest of the fields.
To include newlines in MESSAGE, specify MESSAGE several times.
This is handled as a special case, other fields will be stored
as an array in the journal if they appear multiple times.
--msgid msgid
Sets the RFC 5424 <https://tools.ietf.org/html/rfc5424> MSGID
field. Note that the space character is not permitted inside
of msgid. This option is only used if --rfc5424 is specified
as well; otherwise, it is silently ignored.
-n, --server server
Write to the specified remote syslog server instead of to the
system log socket. Unless --udp or --tcp is specified, logger
will first try to use UDP, but if this fails a TCP connection
is attempted.
--no-act
Causes everything to be done except for writing the log
message to the system log, and removing the connection to the
journal. This option can be used together with --stderr for
testing purposes.
--octet-count
Use the RFC 6587 <https://tools.ietf.org/html/rfc6587> octet
counting framing method for sending messages. When this option
is not used, the default is no framing on UDP, and RFC6587
non-transparent framing (also known as octet stuffing) on TCP.
-P, --port port
Use the specified port. When this option is not specified, the
port defaults to syslog for udp and to syslog-conn for tcp
connections.
-p, --priority priority
Enter the message into the log with the specified priority.
The priority may be specified numerically or as a
facility.level pair. For example, -p local3.info logs the
message as informational in the local3 facility. The default
is user.notice.
--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, local0.info, meaning facility=16 and
level=6, becomes <134>.
If the prefix contains no facility, the facility defaults to
what is specified by the -p option. Similarly, if no prefix is
provided, the line is logged using the priority given with -p.
This option doesn’t affect a command-line message. This option
is primarily designed for use cases where logger is used in a
pipeline (e.g., daemon | logger --prio-prefix) to read
multiple messages with different priorities.
--rfc3164
Use the RFC 3164 <https://tools.ietf.org/html/rfc3164> BSD
syslog protocol to submit messages to a remote server.
--rfc5424[=without]
Use the RFC 5424 <https://tools.ietf.org/html/rfc5424> syslog
protocol to submit messages to a remote server. The optional
without argument can be a comma-separated list of the
following values: notq, notime, nohost.
The notq 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 time
quality is also automatically suppressed when --sd-id
timeQuality is specified.
The notime value (which implies notq) suppresses the complete
sender timestamp that is in ISO-8601 format, including
microseconds and timezone.
The nohost value suppresses gethostname(2) information from
the message header.
The RFC 5424 protocol has been the default for logger since
version 2.26.
-s, --stderr
Output the message to standard error as well as to the system
log. The complete message is output in the same form as sent
to syslog or journald, including priority and possibly other
fields. This option is primarily designed for debugging
purposes and is often used with --no-act.
--sd-id name[@digits]
Specifies a structured data element ID for an RFC 5424 message
header. The option has to be used before --sd-param to
introduce a new element. The number of structured data
elements is unlimited. The ID (name plus possibly @digits) is
case-sensitive and uniquely identifies the type and purpose of
the element. The same ID must not exist more than once in a
message. The @digits part is required for user-defined
non-standardized IDs.
logger currently generates the timeQuality standardized
element only. RFC 5424 also describes the elements origin
(with parameters ip, enterpriseId, software and swVersion) and
meta (with parameters sequenceId, sysUpTime and language).
These element IDs may be specified without the @digits suffix.
--sd-param name=value
Specifies a structured data element parameter, a name and
value pair. The option has to be used after --sd-id and may be
specified more than once for the same element. Note that the
quotation marks around value are required and must be escaped
on the command line.
logger --rfc5424 --sd-id zoo@123 \
--sd-param tiger="hungry" \
--sd-param zebra="running" \
--sd-id manager@123 \
--sd-param onMeeting="yes" \
"this is message"
produces:
<13>1 2015-10-01T14:07:59.168662+02:00 ws kzak - -
[timeQuality tzKnown="1" isSynced="1"
syncAccuracy="218616"][zoo@123 tiger="hungry"
zebra="running"][manager@123 onMeeting="yes"] this is message
-S, --size size
Sets the maximum permitted message size to size. 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 messages larger than 1KiB over any type
of syslog protocol. As such, the --size option affects logger
in all cases (not only when --rfc5424 was used).
Note: the message-size limit limits the overall message size,
including the syslog header. Header sizes vary depending on
the selected options and the hostname length. As a rule of
thumb, headers are usually not longer than 50 to 80
characters. When selecting a 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.
--socket-errors mode
Print errors about Unix socket connections. The mode can be
on, off, or auto. When the mode is auto (the default), then
logger will detect if the init process is systemd(1), and if
so, the assumption is made that /dev/log can be used early at
boot. The lack of /dev/log on other init systems will not
cause errors, just as when using the openlog(3) system call.
The logger(1) before version 2.26 used openlog(3), and thus
was unable to detect the loss of messages sent to Unix
sockets.
When errors are not enabled, lost messages are not
communicated and will result in a successful exit status of
logger(1).
-T, --tcp
Use stream (TCP) only. By default the connection is tried to
the syslog-conn port defined in /etc/services, which is often
601.
See also --server and --socket to specify where to connect.
-t, --tag tag
Mark every line to be logged with the specified tag. The
default tag is the name of the user logged in on the terminal
(or a user name based on effective user ID).
-u, --socket socket
Write to the specified socket instead of to the system log
socket.
--
End the argument list. This allows the message to start with a
hyphen (-).
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
The logger utility exits 0 on success, and >0 if an error occurs.
Valid facility names are:
auth
authpriv for security information of a sensitive nature
cron
daemon
ftp
kern cannot be generated from userspace process, automatically
converted to user
lpr
mail
news
syslog
user
uucp
local0
to
local7
security deprecated synonym for auth
Valid level names are:
emerg
alert
crit
err
warning
notice
info
debug
panic deprecated synonym for emerg
error deprecated synonym for err
warn deprecated synonym for warning
For the priority order and intended purposes of these facilities
and levels, see syslog(3).
The logger command is expected to be IEEE Std 1003.2 ("POSIX.2")
compatible.
logger System rebooted
logger -p local0.notice -t HOSTIDM -f /dev/idmc
logger -n loghost.example.com System rebooted
The logger command was originally written by University of
California in 1983-1993 and later rewritten by Karel Zak
<[email protected]>, Rainer Gerhards <[email protected]>, and
Sami Kerola <[email protected]>.
journalctl(1), syslog(3), systemd.journal-fields(7)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The logger command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) If you discover any
rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to [email protected]
util-linux 2.42-start-521-ec46 2025-08-09 LOGGER(1)
Pages that refer to this page: logger(1), pmie(1), pmpost(1), systemd-cat(1), syslog(3), rsyslog.conf(5), rsyslogd(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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