topic Re: Monitoring Stdout in Operating System - HP-UX

Monitoring Stdout

Scott McDade — Thu, 14 Aug 2003 19:14:15 GMT

I am trying to figure out a way to monitor stdout. I have several C and Perl apps running together on an 11i machine and I am getting some inconsistant behavior and I suspect it may be due to stdout sharing between the 2 progs.

Can anyone tell me how to monitor stdout?

-Scott

Re: Monitoring Stdout

doug mielke — Thu, 14 Aug 2003 19:25:04 GMT

does re direction to file not work when you call the scripts?

Re: Monitoring Stdout

Ralph Grothe — Fri, 15 Aug 2003 05:19:37 GMT

How are the processes communicating with one another?
Is one writing to stdout what the other is reading from its stdin?
What do your pipes look like?

Sometimes buffering is getting in the way and mangling the correct sequence of communication (a common issue in IPC).

I cannot tell what to do in C.
I
n Perl it is advisable to enforce autoflushing in your Perl code by defining the special variable "$|".

Usual Perl idioms to this end are:

$|++;
# or
$| = 1;

# or if you have to flush other file handles
select((select(HANDLE), $|++)[0]);

If you don't mind importing some other code you could also use the IO::Handle (or IO::File, actually inheriting from IO::Handle)module that offer an autoflush method that avoids the arcane select idiom above.