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 514.

              See also --server and --socket to specify where to

       -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.

              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

              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 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 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 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 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 server.

              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 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

              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

       -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

              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

              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

              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

       -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 (-).

       -V, --version
              Display version information and exit.

       -h, --help
              Display help text 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)

AVAILABILITY         top

       The logger command is part of the util-linux package and is
       available from Linux Kernel Archive 

COLOPHON         top

       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
       2021-03-21.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-19.)  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                    November 2015                    LOGGER(1)

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