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
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.
−n, −−serverserver
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.
−−no−act
Causes everything to be done except for writing the log message to the system
log, and removing the connection or the journal.  This option can be used
together with −−stderr for testing purposes.
−−octet−count
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.
−P, −−portport
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, −−prioritypriority
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.
−−rfc3164
Use the RFC 3164 BSD syslog protocol to submit messages to a remote server.
−−rfc5424[=without]
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 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.
−−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−paramname="value"
Specifies a structured data element paramameter, 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.
        .nf
            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"