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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 .

-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 --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 (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.

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.

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.

logger --journald <<end
MESSAGE=The dogs bark, but the caravan goes on.
CARAVAN=goes on

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 will display MESSAGE field. Use journalctl --output json-
pretty to see rest of the fields.

--msgid MSGID
Sets the 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.

Causes everything to be done except for the write the log message to the system
log, remove connection or journal. This options is usable together with --stderr
for testing purpose.

--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 larger than 1KiB message over any type of syslog protocol. As
such, the --size option affects logger in all cases (not only when --rfc5424 was

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.

-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 thist
fails a TCP connection is attempted.

-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

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.

Use the RFC 3164 BSD syslog protocol to submit messages to a remote server.

Use the RFC 5424 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 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.

Use the RFC 6587 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.

-s, --stderr
Output the message to standard error as well as to the system log.

-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.

-t, --tag tag
Mark every line to be logged with the specified tag.

-u, --socket socket
Write to the specified socket instead of to the system log socket.

Print errors about Unix socket connections. The mode can be a value of off, on, or
auto. 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
openlog(3) system call. The logger(1) before version 2.26 used openlog, and hence
was inable to detected loss of messages sent to Unix sockets.

The default mode is auto. When errors are not enabled lost messages are not
communicated and will result to successful return value of logger(1) invocation.

-- End the argument list. This allows the message to start with a hyphen (-).

-V, --version
Display version information and exit.

-h, --help
Display help text and exit.


The logger utility exits 0 on success, and >0 if an error occurs.


Valid facility names are:

authpriv for security information of a sensitive nature
kern cannot be generated from userspace process, automatically converted to user
security deprecated synonym for auth

Valid level names are:


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


logger System rebooted
logger -p local0.notice -t HOSTIDM -f /dev/idmc
logger -n loghost.example.com System rebooted

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