close(n) Tcl (7.5) close(n)
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NAME
close - Close an open channel.
SYNOPSIS
close channelId
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DESCRIPTION
Closes the channel given by channelId. ChannelId must be a
channel identifier such as the return value from a previous
open or socket command. All buffered output is flushed to
the channel's output device, any buffered input is
discarded, the underlying file or device is closed, and
channelId becomes unavailable for use.
If the channel is blocking, the command does not return |
until all output is flushed. If the channel is nonblocking |
and there is unflushed output, the channel remains open and |
the command returns immediately; output will be flushed in |
the background and the channel will be closed when all the |
flushing is complete.
If channelId is a blocking channel for a command pipeline
then close waits for the child processes to complete.
If the channel is shared between interpreters, then close |
makes channelId unavailable in the invoking interpreter but |
has no other effect until all of the sharing interpreters |
have closed the channel. When the last interpreter in which |
the channel is registered invokes close, the cleanup actions |
described above occur. See the interp command for a |
description of channel sharing. |
Channels are automatically closed when an interpreter is |
destroyed and when the process exits. Channels are switched |
to blocking mode, to ensure that all output is correctly |
flushed before the process exits.
The command returns an empty string, and may generate an
error if an error occurs while flushing output.
KEYWORDS
blocking, channel, close, nonblocking
Page 1 (printed 2/19/99)
