Provided by: tcl8.6-doc_8.6.1-4ubuntu1_all bug


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


       fblocked channelId


       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

       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.


       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


       gets(3tcl), open(3tcl), read(3tcl), socket(3tcl), Tcl_StandardChannels(3tcl)


       blocking, nonblocking