null(n) 2.2 "Memory channels"

NAME

null - Create and manipulate null channels

TABLE OF CONTENTS

    TABLE OF CONTENTS
    SYNOPSIS
    DESCRIPTION
    OPTIONS
    SEE ALSO
    KEYWORDS
    COPYRIGHT

SYNOPSIS

package require Tcl
package require memchan

null

DESCRIPTION

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

null
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.

OPTIONS

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

-delay ?milliseconds?
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.

SEE ALSO

fifo, fifo2, memchan, random, zero

KEYWORDS

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

COPYRIGHT

Copyright © 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>