Dear Perl Monk,

A few days ago I posted a question "close STDOUT does not work, why?" at close STDOUT does not work, why?

and BrowserUK pointed out that I needed to close STDIN and STDERR as well and it made the redirection worked. However, when I tried to invoke an external program using PIPE later in my program, it failed. Below is a piece of code I wrote to demonstrate my problem. Any thoughts?

#!/usr/bin/perl

use CGI qw(:standard);
$| = 1;

if (my $pid = fork) {    #parent does
close STDOUT;
close STDIN;
close STDERR;
open STDIN,     '<', '/dev/null';
open STDOUT,    '>', '/dev/null';
my $err_file = "/var/www/html/cgi_data/error_log";
open STDERR,    '>', $err_file;
start_x();
}

else
{
  print header(), q~
<HTML>
<HEAD>
<META HTTP-EQUIV="Refresh" CONTENT="3; URL=/cgi_data/page1.html">
<TITLE>New Site notification</TITLE>
</HEAD>
<BODY>My homepage has moved to a new location. I am here</BODY></HTML>
~;
exit;
} 


sub start_x
{
    $com = "./myprog 100";
    open PIPE, "$com |";
    $outfile1 = "../html/cgi_data/page2.html";
    open OUT, ">$outfile1" or die "Can not open for write: $outfile";
   while ($data = <PIPE>)
    {
        print OUT "$data\n";
    }
   close OUT;
}

[download]

The problem occurs at 
open PIPE, "$com |";

[download]

I tried to put a print STDERR "I am here"; and noticed it does print to the error_log file if I put the print statement above the open PIPE but does not if I put the print statement after it. Any thoughts?
Thanks.

Code tags added by GrandFather

In reply to Closing STDIO Caused Pipe Not To Work by Anonymous Monk

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