Index for Section 5

Alphabetical listing for L

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LISTEN()
NAME
  LISTEN - listen for a notification

SYNOPSIS
  LISTEN name

DESCRIPTION
  LISTEN registers the current session as a listener on the notification
  condition name.  If the current session is already registered as a listener
  for this notification condition, nothing is done.

  Whenever the command NOTIFY name is invoked, either by this session or
  another one connected to the same database, all the sessions currently
  listening on that notification condition are notified, and each will in
  turn notify its connected client application. See the discussion of NOTIFY
  for more information.

  A session can be unregistered for a given notify condition with the
  UNLISTEN command. A session's listen registrations are automatically
  cleared when the session ends.

  The method a client application must use to detect notification events
  depends on which PostgreSQL application programming interface it uses. With
  the libpq library, the application issues LISTEN as an ordinary SQL
  command, and then must periodically call the function PQnotifies to find
  out whether any notification events have been received. Other interfaces
  such as libpgtcl provide higher-level methods for handling notify events;
  indeed, with libpgtcl the application programmer should not even issue
  LISTEN or UNLISTEN directly. See the documentation for the interface you
  are using for more details.

  NOTIFY [notify(5)] contains a more extensive discussion of the use of
  LISTEN and NOTIFY.

PARAMETERS
  name Name of a notify condition (any identifier).

EXAMPLES
  Configure and execute a listen/notify sequence from psql:

  LISTEN virtual;
  NOTIFY virtual;
  Asynchronous notification "virtual" received from server process with PID 8448.

COMPATIBILITY
  There is no LISTEN statement in the SQL standard.

SEE ALSO
  NOTIFY [notify(5)], UNLISTEN [unlisten(l)]

Index for Section 5

Alphabetical listing for L

Top of page