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 available 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 without 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(3tcl), open(3tcl), read(3tcl), socket(3tcl), Tcl_StandardChannels(3tcl)

KEYWORDS

       blocking, nonblocking