Manual Pages for UNIX Operating System command usage for man close

Tcl Built-In Commands                                   close(1T)



_________________________________________________________________

NAME
     close - Close an open channel.

SYNOPSIS
     close channelId
_________________________________________________________________


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  dev-
     ice, 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 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 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.  If a com-
     mand in a command pipeline  created  with  open  returns  an
     error,  close  generates  an error (similar to the exec com-
     mand.)




Tcl                     Last change: 7.5                        1






Tcl Built-In Commands                                   close(1T)



EXAMPLE
     This illustrates how you can use Tcl to  ensure  that  files
     get closed even when errors happen 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(1T),       open(1T),        socket(1T),        eof(1T),
     Tcl_StandardChannels(3TCL)


KEYWORDS
     blocking, channel, close, nonblocking

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:

     _______________________________________
    |   ATTRIBUTE TYPE   |  ATTRIBUTE VALUE|
    |____________________|__________________|_
    | Availability       |  runtime/tcl-8  |
    |____________________|__________________|_
    | Interface Stability|  Uncommitted    |
    |____________________|_________________|

NOTES
     Source for Tcl is available on http://opensolaris.org.


















Tcl                     Last change: 7.5                        2