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.

       -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 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 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

       -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

       -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 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

       --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 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
              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 (-).

       -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

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
       2020-11-01.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-10-21.)  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

util-linux                      November 2015                      LOGGER(1)

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