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.
Use datagrams (UDP) only. By default the connection is tried to
the syslog port defined in /etc/services, which is often 514 .
Ignore empty lines when processing files. An empty line is
defined to be a line without any characters. Thus a line con-
sisting 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
-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 recom-
mended 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 ignored.
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 sys-
temd.journal-fields(7) for details. The use of a MESSAGE_ID
field is generally a good idea, as it makes finding entries
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 fields.
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
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 pur-
Use the RFC 6587 octet counting framing method for sending mes-
sages. 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 con-
-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 informa-
tional 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 con-
structed 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
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 speci-
The notime value (which implies notq) suppresses the complete
sender timestamp that is in ISO-8601 format, including microsec-
onds and timezone.
The nohost value suppresses gethostname(2) information from the
The RFC 5424 protocol has been the default for logger since ver-
Output the message to standard error as well as to the system
Specifies a structured data element ID for an RFC 5424 message
header. The option has to be used before --sd-param to intro-
duce a new element. The number of structured data elements is
unlimited. The ID (name plus possibly @digits) is case-sensi-
tive and uniquely identifies the type and purpose of the ele-
ment. The same ID must not exist more than once in a message.
The @digits part is required for user-defined non-standardized
logger currently generates the timeQuality standardized element
only. RFC 5424 also describes the elements origin (with parame-
ters 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 speci-
fied more than once for the same element. Note that the quota-
tion marks around value are required and must be escaped on the
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
Sets the maximum permitted message size to size. The default is
1KiB characters, which is the limit traditionally used and spec-
ified in RFC 3164. With RFC 5424, this limit has become flexi-
ble. 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 Unix sockets.
The default mode is auto. When errors are not enabled lost mes-
sages are not communicated and will result to successful return
value of logger(1) invocation.
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
Display version information and exit.
Display help text and exit.
The logger utility exits 0 on success, and >0 if an error occurs.
FACILITIES AND LEVELS
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 syslog(3).
logger System rebooted
logger -p local0.notice -t HOSTIDM -f /dev/idmc
logger -n loghost.example.com System rebooted
journalctl(1), syslog(3), systemd.journal-fields(7)
The logger command is expected to be IEEE Std 1003.2 ("POSIX.2") com-
The logger command is part of the util-linux package and is available
from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-
util-linux November 2015 LOGGER(1)
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