Re: Re: Pipe, fork, exec and red-hot pokers.

This may be a long shot, but *how* are you reading that output? are you using the diamond operator, or are you reading via select(IO::Select) + read/sysread ? It may not have anything to do with your problem at all, but who knows...

FWIW, something like the following works for me

# note: this code will go into infinite loop
# and is not a particularly good piece of code...
use IO::Handle;
use IO::Select;

my( $readfh, $writefh ) = ( IO::Handle->new(), IO::Handle->new() );

pipe( $readfh, $writefh );

if( my $pid = fork() ) {
    $writefh->close();
    my $select = IO::Select->new( $readfh );
    my $buf;
    while( 1 ) {
        if( $select->can_read( 1 ) ) {
            if( read( $readfh, $buf, 4096, 0 ) ) {
                print "got '$buf'";
            }
        }
    }
} else {
    $readfh->close;

    open( STDOUT, sprintf( '>&%d', $writefh->fileno ) );
    STDOUT->autoflush(1);

    exec( 'find', '/usr/local/lib/perl5' );
}
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Comment on Re: Re: Pipe, fork, exec and red-hot pokers. Download Code

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Re: Re: Re: Pipe, fork, exec and red-hot pokers. by hagus (Monk) on Apr 09, 2002 at 00:49 UTC
First, I changed 'read' to 'sysread'. But if the program you are exec()ing is this: `#!/usr/bin/perl my $i=0; while (1) { print "stdout " . $i++ . "\n"; sleep 1; }` [download] Then you will find that no output is captured by read. The perl program must set $\|=1, which is exactly what I don't want to have to worry about. -- Ash OS durbatulk, ash OS gimbatul, Ash OS thrakatulk, agh burzum-ishi krimpatul! Uzg-Microsoft-ishi amal fauthut burguuli.	[reply] [d/l]

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Re: Re: Re: Pipe, fork, exec and red-hot pokers.
by hagus (Monk) on Apr 09, 2002 at 00:49 UTC

#!/usr/bin/perl

my $i=0;
while (1)
{
    print "stdout " . $i++ . "\n";
    sleep 1;
}
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--
Ash OS durbatulk, ash OS gimbatul,
Ash OS thrakatulk, agh burzum-ishi krimpatul!
Uzg-Microsoft-ishi amal fauthut burguuli.

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