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close(n) Tcl Built-In Commands 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 an identifier for an open channel such as a Tcl standard channel (stdin,
stdout, or stderr), the return value from an invocation of open or socket, or the result
of a channel creation command provided by a Tcl extension.
All buffered output is flushed to the channel's output device, any buffered input is dis-
carded, 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. If a command in a command pipeline created with open returns an error,
close generates an error (similar to the exec command.)
EXAMPLE
This illustrates how you can use Tcl to ensure that files get closed even when errors hap-
pen by combining catch, close and return:
proc withOpenFile {filename channelVar script} {
upvar 1 $channelVar chan
set chan [open $filename]
catch {
uplevel 1 $script
} result options
close $chan
return -options $options $result
}
SEE ALSO
file(n), open(n), socket(n), eof(n), Tcl_StandardChannels(3)
KEYWORDS
blocking, channel, close, nonblocking
Tcl 7.5 close(n)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2024-04-16 02:11 @3.149.234.230 CrawledBy claudebot