logger(1) — Linux manual page


LOGGER(1)                     User Commands                    LOGGER(1)

NAME         top

       logger - enter messages into the system log

SYNOPSIS         top

       logger [options] message

DESCRIPTION         top

       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         top

       -d, --udp
           Use datagrams (UDP) only. By default the connection is tried
           to the syslog port defined in /etc/services, which is often

           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.

           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. Examples:

                  logger --journald <<end
                  MESSAGE=The dogs bark, but the caravan goes on.
                  CARAVAN=goes on

                  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

       --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.

           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.

           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.

           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

           This option doesn’t affect a command-line message.

           Use the RFC 3164 <https://tools.ietf.org/html/rfc3164> BSD
           syslog protocol to submit messages to a remote server.

           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

       --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"


           <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, 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

           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

           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         top

       The logger utility exits 0 on success, and >0 if an error occurs.


       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).

CONFORMING TO         top

       The logger command is expected to be IEEE Std 1003.2 ("POSIX.2")

EXAMPLES         top

          logger System rebooted

          logger -p local0.notice -t HOSTIDM -f /dev/idmc

          logger -n loghost.example.com System rebooted

AUTHORS         top

       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         top

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

REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       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/>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
       a bug report for this manual page, send it to
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2024-06-14. (At that time, the date of the most recent commit
       that was found in the repository was 2024-06-10.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to man-pages@man7.org

util-linux 2.39.594-1e0ad      2023-07-19                      LOGGER(1)

Pages that refer to this page: logger(1)pmie(1)pmpost(1)systemd-cat(1)syslog(3)rsyslog.conf(5)rsyslogd(8)