osx man page for flush

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

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NAME
       flush - Flush buffered output for a channel

SYNOPSIS
       flush channelId
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DESCRIPTION
       Flushes any output that has been buffered for channelId.

       ChannelId  must be an identifier for an open channel such as a Tcl standard channel (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.  The channel must have been opened for writing.

       If the channel is in blocking mode the command does not return until all the buffered output has been flushed to the channel. If the  chan-
       nel  is in nonblocking mode, the command may return before all buffered output has been flushed; the remainder will be flushed in the back-
       ground as fast as the underlying file or device is able to absorb it.

EXAMPLE
       Prompt for the user to type some information in on the console:
	      puts -nonewline "Please type your name: "
	      flush stdout
	      gets stdin name
	      puts "Hello there, $name!"

SEE ALSO
       file(n), open(n), socket(n), Tcl_StandardChannels(3)

KEYWORDS
       blocking, buffer, channel, flush, nonblocking, output

Tcl									7.5								  flush(n)