mojave man page for fblocked

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

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NAME
       fblocked - Test whether the last input operation exhausted all available input

SYNOPSIS
       fblocked channelId
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DESCRIPTION
       The  fblocked command returns 1 if the most recent input operation on channelId returned less information than requested because all avail-
       able input was exhausted.  For example, if gets is invoked when there are only three characters available  for  input  and  no  end-of-line
       sequence, gets returns an empty string and a subsequent call to fblocked will return 1.

       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.

EXAMPLE
       The fblocked command is particularly useful when writing network servers, as it allows you to write your code in a line-by-line style with-
       out preventing the servicing of other connections.  This can be seen in this simple echo-service:

	      # This is called whenever a new client connects to the server
	      proc connect {chan host port} {
		  set clientName [format <%s:%d> $host $port]
		  puts "connection from $clientName"
		  fconfigure $chan -blocking 0 -buffering line
		  fileevent $chan readable [list echoLine $chan $clientName]
	      }

	      # This is called whenever either at least one byte of input
	      # data is available, or the channel was closed by the client.
	      proc echoLine {chan clientName} {
		  gets $chan line
		  if {[eof $chan]} {
		      puts "finishing connection from $clientName"
		      close $chan
		  } elseif {![fblocked $chan]} {
		      # Didn't block waiting for end-of-line
		      puts "$clientName - $line"
		      puts $chan $line
		  }
	      }

	      # Create the server socket and enter the event-loop to wait
	      # for incoming connections...
	      socket -server connect 12345
	      vwait forever

SEE ALSO
       gets(n), open(n), read(n), socket(n), Tcl_StandardChannels(3)

KEYWORDS
       blocking, nonblocking

Tcl									7.5							       fblocked(n)