logger - enter messages into the system log
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
- 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.
- 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.
Note that the system logging infrastructure (for example systemd when
listening on /dev/log) may follow local socket credentials to overwrite
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
- 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.
- 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
- --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
- -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.
- 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.
- 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, --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.
- 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
- 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
The nohost value suppresses gethostname(2) information from
the message header.
- The RFC 5424 protocol has been the default for logger since version
- -s, --stderr
- Output the message to standard error as well as to the system log.
- 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.
- 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"
<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.
- 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 unable to detected loss of messages sent to
- The default mode is auto. When errors are not enabled lost messages
are not communicated and will result to successful return value of
- -T, --tcp
- Use stream (TCP) only. By default the connection is tried to the
syslog-conn port defined in /etc/services, which is often
- -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
- End the argument list. This allows the message to start with a
- -V, --version
- Display version information and exit.
- -h, --help
- Display help text and exit.
utility exits 0 on success, and >0 if an error occurs.
Valid facility names are:
||for security information of a sensitive nature
||cannot be generated from userspace process, automatically converted
||deprecated synonym for auth
Valid level names are:
||deprecated synonym for emerg
||deprecated synonym for err
||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
command is expected to be IEEE Std 1003.2
The logger command is part of the util-linux package and is available from