Hi, well I did some digging and came up with a method from "perldoc -f filehandle". It is from "how to read a byte from a filehandle". I did come up with an error at first telling me that my cdefs.ph file had a bunch syntax errors between ") (". I wonder if this is a bug in 5.8? The lines in question all needed a comma between the ") (" .

A typical line needing the comma is

if(defined (defined(&__cplusplus) ? &__cplusplus : 0) && (defined(&__GNUC_PREREQ) ? &__GNUC_PREREQ : 0), (2,8)) {

Notice the comma I inserted between 0) and (2,8)).

Anyways, after fixing that, the following code does what I was looking for. :-) 

#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
require 'sys/ioctl.ph';

#interface to "bc" calculator 
my $pid = open3(\*WRITE, \*READ,\*ERROR,"bc");
            #if \*ERROR is false, STDERR is sent to STDOUT  

my($error,$answer)=('','');

while(1){

print "Enter expression for bc, i.e. 2 + 2\n";
chomp(my $query = <STDIN>);

#send query to bc 
print WRITE "$query\n";

#timing delay needed tp let bc output 
select(undef,undef,undef,.01);

#see which filehandles have output from perldoc -q filehandle 
my $esize = pack("L", 0);
ioctl(\*ERROR, FIONREAD(), $esize) or die "Couldn't call ioctl: $!\n";
$esize = unpack("L", $esize);
print "esize-> $esize\n";

my $rsize = pack("L", 0);
ioctl(\*READ, FIONREAD(), $rsize) or die "Couldn't call ioctl: $!\n";
$rsize = unpack("L", $rsize);
print "rsize-> $rsize\n";


#get the output from bc 
if($esize > 0){sysread(ERROR,$error,$esize); print "Error-> $error\n"}
if($rsize > 0){sysread(READ,$answer,$rsize); print "Output->$query = $
+answer\n"}

($error,$answer,$rsize,$esize)=('','',0,0);
}

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In reply to Re: Re: IPC::Open3 and blocking filehandles by zentara
in thread IPC::Open3 and blocking filehandles by zentara

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