***COMMAND***
close - Close an open channel

***USAGE***
'''close''' channelId

***CONTEXT***
TCL core command
 
***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. 
 
***MAN PAGE***
http://www.tcl.tk/man/tcl8.5/TclCmd/close.htm
 
***SEE ALSO***
[file], [open], [socket], [eof], [channel], [exec], [stderr]

***EXAMPLES***

 set fh [open output.txt r]
 set data [read $fh]
 close $fh

----
[LV] What are the ramifications if you don't close a file in Tcl?  Any?
I assume a memory leak in long running ''[daemon]'' type apps...
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[glennj]: When working with pipes (i.e. [[set pipe [[open "| some command"]]]]),  and the pipe is blocking (i.e. [[fconfigure $pipe -blocking yes]] which is the default), then [[close $pipe]] throws an error if the command exited with non-zero status or if the command sent any output to stderr.

example:
 set command {sh -c {echo "to stdout"; echo >&2 "to stderr"; exit 42}}
 set pipe [open "| $command"]
 set standard_output [read -nonewline $pipe]
 set exit_status 0
 if {[catch {close $pipe} standard_error] != 0} {
     global errorCode
     if {"CHILDSTATUS" == [lindex $errorCode 0]} {
         set exit_status [lindex $errorCode 2]
     }
 }
 puts "exit status is $exit_status"
 puts "captured standard output: {$standard_output}"
 puts "captured standard error: {$standard_error}"

Output is:
 exit status is 42
 captured standard output: {to stdout}
 captured standard error: {to stderr}

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[AMG]: TIP #332 "Half-Close for Bidirectional Channels" [http://tip.tcl.tk/332] adds an optional argument to specify which direction of the channel to close, like the shutdown(2) system call [http://linux.die.net/man/2/shutdown].

'''close''' ''channel'' ?'''read'''|'''write'''?

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