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



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NAME
     close - Close an open channel.

SYNOPSIS
     close _c_h_a_n_n_e_l_I_d
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DESCRIPTION
     Closes the channel given by _c_h_a_n_n_e_l_I_d.  _C_h_a_n_n_e_l_I_d 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 dis-
     carded, the underlying file or device is closed,  and  _c_h_a_n_-
     _n_e_l_I_d 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 _c_h_a_n_n_e_l_I_d 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  _c_h_a_n_n_e_l_I_d 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 descrip-  |
     tion 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








Tcl                     Last change: 7.5                        1