showConnections             package:base             R Documentation

Display Connections

Description:

     Display aspects of connections.

Usage:

     showConnections(all=FALSE)
     getConnection(what)
     closeAllConnections()

     stdin()
     stdout()
     stderr()

Arguments:

     all: logical: if true all connections, including closed ones and
          the standard ones are displayed. If false only open
          user-created connections are included.

    what: integer: a row number of the table given by
          `showConnections'.

Details:

     `stdin()', `stdout()' and `stderr()' are standard connections
     corresponding to input, output and error on the console
     respectively (and not necessarily to file streams).  They are
     text-mode connections of class `"terminal"' which cannot be opened
     or closed, and are read-only, write-only and write-only
     respectively. The `stdout()' and `stderr()' connections can be
     re-directed by `sink'.

     `showConnections' returns a matrix of information.  If a
     connection object has been lost or forgotten, `getConnection' will
     take a row number from the table and return a connection object
     for that connection, which can be used to close the connection,
     for example.

     `closeAllConnections' closes (and destroys) all open user
     connections, restoring all `sink' diversions as it does so.

Value:

     `stdin()', `stdout()' and `stderr()' return connection objects.

     `showConnections' returns a character matrix of information with a
     row for each connection, by default only for open non-standard
     connections.

     `getConnection' returns a connection object, or `NULL'.

See Also:

     `connections'

Examples:

     showConnections(all = TRUE)

     textConnection(letters)
     # oops, I forgot to record that one
     showConnections()
     #  class     description      mode text   isopen   can read can write
     #3 "letters" "textConnection" "r"  "text" "opened" "yes"    "no"     
     close(getConnection(3))

     showConnections()

