1close(n)                     Tcl Built-In Commands                    close(n)
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NAME

8       close - Close an open channel.
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SYNOPSIS

11       close channelId
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DESCRIPTION

16       Closes the channel given by channelId.
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18       ChannelId must be an identifier for an open channel such as a Tcl stan‐ │
19       dard channel (stdin, stdout, or stderr), the return value from an invo‐ │
20       cation  of  open or socket, or the result of a channel creation command │
21       provided by a Tcl extension.
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23       All buffered output is flushed to  the  channel's  output  device,  any
24       buffered  input  is discarded, the underlying file or device is closed,
25       and channelId becomes unavailable for use.
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27       If the channel is blocking, the command does not return until all  out‐ │
28       put  is  flushed.  If the channel is nonblocking and there is unflushed │
29       output, the channel remains open and the command  returns  immediately; │
30       output will be flushed in the background and the channel will be closed │
31       when all the flushing is complete.
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33       If channelId is a blocking channel for a command  pipeline  then  close
34       waits for the child processes to complete.
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36       If  the  channel is shared between interpreters, then close makes chan‐ │
37       nelId unavailable in the invoking interpreter but has no  other  effect │
38       until  all  of  the sharing interpreters have closed the channel.  When │
39       the last interpreter in which the channel is registered invokes  close, │
40       the cleanup actions described above occur. See the interp command for a │
41       description of channel sharing.                                         │
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43       Channels are automatically closed when an interpreter is destroyed  and │
44       when  the  process  exits.   Channels are switched to blocking mode, to │
45       ensure that all output is correctly flushed before the process exits.
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47       The command returns an empty string, and may generate an  error  if  an
48       error occurs while flushing output.  If a command in a command pipeline
49       created with open returns an error, close generates an  error  (similar
50       to the exec command.)
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EXAMPLE

53       This  illustrates  how  you can use Tcl to ensure that files get closed
54       even when errors happen by combining catch, close and return:
55              proc withOpenFile {filename channelVar script} {
56                  upvar 1 $channelVar chan
57                  set chan [open $filename]
58                  catch {
59                      uplevel 1 $script
60                  } result options
61                  close $chan
62                  return -options $options $result
63              }
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SEE ALSO

67       file(n), open(n), socket(n), eof(n), Tcl_StandardChannels(3)
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KEYWORDS

71       blocking, channel, close, nonblocking
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75Tcl                                   7.5                             close(n)
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