[boulder.pm] unblocked pipes

[Amar Vattakandy]

Finally, found the solution. Thanx to you guys.. And the answer is in
setting the
non bocking flag on fctl. Here is a snippet of code, if any one fall into
the same pit
that I was in for the last couple of days.

==
use Tk ;
use Socket ;
use Fcntl ;
use Tk::FileSelect ;
use IO::Handle;
require Tk::Dialog;

# Open the pipes for communication between the background process
# and the GUI
socketpair(BKGROUND,GUI,AF_UNIX,SOCK_STREAM,PF_UNSPEC) or die "Bad
Socketpair $!";
$SockFlags = '';
fcntl(BKGROUND,F_GETFL,$SockFlags) or die "Cant get Flags: $!";
$SockFlags |= O_NONBLOCK;
fcntl(BKGROUND,F_SETFL,$SockFlags) or die "Cant set Flags: $!";
fcntl(GUI,F_GETFL,$SockFlags) or die "Cant get Flags: $!";
$SockFlags |= O_NONBLOCK;
fcntl(GUI,F_SETFL,$SockFlags) or die "Cant set Flags: $!";
BKGROUND ->autoflush(1);
GUI ->autoflush(1);
==
Now, the forked processes could talk to each other like
$blahFromGUI = <GUI> ;
or
printf (GUI "$blahToGUI \n");
etc...
Call me stupid, but I had lost a lot of time debugging apps with no \n in
their
messages and expected the autoflush to work..

Anyway, the rest of the code from the background process

while (1)
   {
       $blahFromGUI = <GUI>;
        if (defined $blahFromGUI)
          {
            chomp($blahFromGUI);
            printf("Child: Got $blahFromGUI\n");
          }
        else
          {
            printf("Child Did Not Receive Anything \n");
          }
        sleep 1 ;
      }

Hoping someone would find it useful..

Amar Vattakandy wrote:

> Any help on this would be appreciated:
>
> | I have a parent and a child (thru forking) that needs to talk to each
>  | other thru a
>  | socket pair pipe. Communication works fine, but the problem happens
> when
>  | I try
>  | to read from a pipe that has no data in it. The read, which is like
>  |  $readline = <CHILD> ;
>  | keeps waiting till the child has some data in it. I know that this is
>
>  | how it is supposed
>  | to work, but is there any way I could check whether there is some
> data
>  | in the pipe
>  | before I read the pipe ?
>  |
>  | Thanx
>  | Amar
>
> --
>
>        *********************************
>                Amar Salaj V
>        National Semiconductor Corporation
>               1351 S Sunset St.
>               Longmont CO-80501
>
>              Ph   : 303 774 5181
>              Fax  : 303 774 5801
>
>        *********************************

--

       *********************************
               Amar Salaj V
       National Semiconductor Corporation
              1351 S Sunset St.
              Longmont CO-80501

             Ph   : 303 774 5181
             Fax  : 303 774 5801

       *********************************