util-linux/misc-utils/logger.1.adoc

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	@(#)logger.1	8.1 (Berkeley) 6/6/93
////
= logger(1)
:doctype: manpage
:man manual: User Commands
:man source: util-linux {release-version}
:page-layout: base
:command: logger

== 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 link:https://tools.ietf.org/html/rfc5424[RFC 5424] 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 link:https://tools.ietf.org/html/rfc6587[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*.

*--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 link:https://tools.ietf.org/html/rfc3164[RFC 3164] BSD syslog protocol to submit messages to a remote server.

*--rfc5424*[**=**__without__]::
Use the link:https://tools.ietf.org/html/rfc5424[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-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 (-).

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== 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 mailto:kzak@redhat.com[Karel Zak], mailto:rgerhards@adiscon.com[Rainer Gerhards], and mailto:kerolasa@iki.fi[Sami Kerola].

== SEE ALSO

*journalctl*(1),
*syslog*(3),
*systemd.journal-fields*(7)

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