NAME

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

SYNOPSIS

       fblocked channelId
_________________________________________________________________

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