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'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: close.n,v 1.1.1.1 2002-01-16 10:25:24 markom Exp $
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'\"
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.so man.macros
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.TH close n 7.5 Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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close \- Close an open channel.
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.SH SYNOPSIS
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\fBclose \fIchannelId\fR
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.BE
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.SH DESCRIPTION
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.PP
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Closes the channel given by \fIchannelId\fR. \fIChannelId\fR must be a
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channel identifier such as the return value from a previous \fBopen\fR
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or \fBsocket\fR command.
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All buffered output is flushed to the channel's output device,
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any buffered input is discarded, the underlying file or device is closed,
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and \fIchannelId\fR becomes unavailable for use.
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.VS "" br
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.PP
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If the channel is blocking, the command does not return until all output
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is flushed.
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If the channel is nonblocking and there is unflushed output, the
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channel remains open and the command
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returns immediately; output will be flushed in the background and the
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channel will be closed when all the flushing is complete.
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.VE
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.PP
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If \fIchannelId\fR is a blocking channel for a command pipeline then
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\fBclose\fR waits for the child processes to complete.
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.VS "" br
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.PP
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If the channel is shared between interpreters, then \fBclose\fR
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makes \fIchannelId\fR unavailable in the invoking interpreter but has no
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other effect until all of the sharing interpreters have closed the
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channel.
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When the last interpreter in which the channel is registered invokes
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\fBclose\fR, the cleanup actions described above occur. See the
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\fBinterp\fR command for a description of channel sharing.
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.PP
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Channels are automatically closed when an interpreter is destroyed and
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when the process exits. Channels are switched to blocking mode, to ensure
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that all output is correctly flushed before the process exits.
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.VE
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.PP
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The command returns an empty string, and may generate an error if
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an error occurs while flushing output.
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.SH KEYWORDS
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blocking, channel, close, nonblocking
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