LOGGER(1) User Commands LOGGER(1)
NAME
logger - enter messages into the system log
SYNOPSIS
logger [options] message
DESCRIPTION
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.
OPTIONS
-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
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.
--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.
--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.
--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 a value
of off, on, or auto. When the mode is auto, then logger will detect
if the init process is systemd(1), 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(3), and hence was unable 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 exit status of
logger(1) invocation.
-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
Print version and exit.
EXIT STATUS
The logger utility exits 0 on success, and >0 if an error occurs.
FACILITIES AND LEVELS
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).
CONFORMING TO
The logger command is expected to be IEEE Std 1003.2 ("POSIX.2")
compatible.
EXAMPLES
logger System rebooted logger -p local0.notice -t HOSTIDM -f /dev/idmc
logger -n loghost.example.com System rebooted
AUTHORS
The logger command was originally written by University of California
in 1983-1993 and later rewritten by Karel Zak <kzak@redhat.com>, Rainer
Gerhards <rgerhards@adiscon.com>, and Sami Kerola <kerolasa@iki.fi>.
SEE ALSO
journalctl(1), syslog(3), systemd.journal-fields(7)
REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
AVAILABILITY
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/>.
util-linux 2.38.1 2022-05-11 LOGGER(1)
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