man sock close

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 a channel
       identifier such as the return value from a previous open or socket com-
       mand.   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 out- |
       put 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  chan- |
       nelId  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 en- |
       sure 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

Tcl                                   7.5                             close(n)