null(n) null(n) 







null - Create and manipulate null channels








package require Tcl 


package require memchan 


null












The command described here is only available in a not-yet released
    version of the package. Use the CVS to get the sources.



  

  
creates a null channel which absorbs everything written into it. Reading
      from it is not possible, or rather will always return zero bytes. These
      channels are essentially Tcl-specific variants of the null device for
      unixoid operating systems (/dev/null). Transfering the generated channel
      between interpreters is possible but does not make much sense.










Memory channels created by null provide one additional
    option to set or query.



  

  
A null channel is always writable and readable. This means that all
      fileevent-handlers will fire continuously. To avoid starvation of
      other event sources the events raised by this channel type have a
      configurable delay. This option is set in milliseconds and defaults to
    5.




A null channel is always writable and never readable. This means
    that a writable fileevent-handler will fire continuously and a
    readable fileevent-handler never at all. The exception to the latter
    is only the destruction of the channel which will cause the delivery of an
    eof event to a readable handler.








fifo, fifo2, memchan, random, zero








channel, i/o, in-memory channel, null








Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>








  

    2.2
    Memory channels