Re^2: Perl won't Open() when called from Java

I was able to fix this but can't understand why. I replaced:

my $syslog_file = "tail -n 0 -f /var/log/messages | "; 
print STDOUT "some debug line: $syslog_file\n";
open(FH,"syslog_file")
print STDOUT "didn't reach before\n";
[download]

with:

my $syslog_file = "tail -n 0 -f /var/log/messages | "; 
print STDERR "some debug line: $syslog_file\n";
open(FH,"syslog_file")
print STDERR "reaches now\n";
[download]

Why would changing to STDERR make a difference?

Comment on Re^2: Perl won't Open() when called from Java Select or Download Code

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Re^3: Perl won't Open() when called from Java by Anonymous Monk on Feb 23, 2012 at 19:35 UTC
Oh I see. STDERR is unbuffered, but STDOUT buffers. Thanks!	[reply]
Re^4: Perl won't Open() when called from Java by Marshall (Canon) on Feb 23, 2012 at 19:56 UTC
Yes, that's right. A typical value for the buffer would be 4K. Mileage varies of course! But it it is completely conceivable that since the program is "hung" that there are unprinted things in the buffer.	[reply]
Re^5: Perl won't Open() when called from Java by ikegami (Patriarch) on Feb 23, 2012 at 20:22 UTC
It was a hardcoded 4K until recently (5.14?). IIRC, now it's configurable at build time, with a default of 8K	[reply]
Re^6: Perl won't Open() when called from Java by Marshall (Canon) on Feb 24, 2012 at 08:29 UTC