Thorney has asked for the wisdom of the Perl Monks concerning the following question:

Hello! Firstly let me say great site! I have been trying to learn a bit about perl today as my weapon of choice php has let me down. That said this could be a very amateur attempt at perl. Anywho the problem I face is when piping emails to a php script (using cpanel) php produces an error: PHP Warning:  Module 'eAccelerator' already loaded in Unknown on line 0 Now unfortunately the MTA interprets any output as a failed send thus returning mail to sender. From www.somacon.com/p520.php it looks like the errors indicate that dynamic extensions are being loaded via .ini files, even though they are already compiled into the PHP binary. Clearly the ideal solution involves not loading the module twice but I do not have the privileges on the shared server to change this. I have tried piping the emails to | /path/myscript.php > null and to | /path/myscript >> null and a few other variations. I have tried putting a q flag on the php shebang. I have tried turning the error reporting down with: error_reporting(E_ERROR); I have tried object buffering in php. But to no avail as the error appears to be produced either on the hashbang or before it. The script now has no extension. I should point out that it runs the entire php script properly. So getting finally to the point I had an idea that a non php script between the MTA and the php might be able to discard (or rather log) any errors to prevent a (false) email undelivered message. Now after a fast tutorial to perl I hacked this together: 
#!/usr/bin/perl
$pipestring = "|./home/bevs/bin/email >> /dev/null";
open STDOUT, '>/dev/null' or die "Can't write to /dev/null: $!";
$SIG{PIPE} = 'IGNORE';
open(FH, $pipestring) or die "can't fork: $!";
while(<STDIN>)
{
my $line = $_;
print FH $line or die "can't write: $!";
}
close FH or die "can't close: $!";

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Now it just pipes the email to my php script but unfortunately the same old error gets output to the MTA and the mail is (supposedly) undelivered. So how pray tell do I take the output of the php and throw it anywhere but where its currently going?

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Re: Silencing errors in a php script using perl nd pipes.
by ikegami (Patriarch) on Jun 20, 2008 at 07:01 UTC
    The error is probably being sent to STDERR, not STDOUT

    Native Bourne shell: 

    #!/bin/sh
exec ./home/bevs/bin/email >/dev/null 2>&1

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    Bourne shell via Perl: 

    #!/usr/bin/perl
exec './home/bevs/bin/email >/dev/null 2>&1';
die;

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    Native Perl: 

    #!/usr/bin/perl

use strict;
use warnings;

use IPC::Open3 qw( open3 );

open(my $fr_chld, '>', '/dev/null')
   or die;

my $pid = open3(\*STDIN, $fr_chld, $fr_chld, './home/bevs/bin/email');

waitpid($pid, 0)
   or die;

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      Thanks very much for your helpful reply! I tried the native bourne shell and it worked. I did try the 2nd option for interests sake and although it didn't output an error it also didn't run my php script on the email. Could you shed any light on why the STDIN is not routed to the php when executed from perl?
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        I'm guessing that the Perl script's STDOUT and STDERR are getting closed, sending a SIGPIPE to the email server, making it think the child exited. I don't know why it doesn't occur for the first snippet.

        It could be prevented by replacing exec with system if I'm right about the cause. Don't forget to make the call to die conditional or remove it for testing.

        A better system would expand on the third snippet to filter out the expected message while letting anything else through. Turns out it's pretty simple since we don't have to deal with the child's STDOUT, just its STDERR. 

        #!/usr/bin/perl

use strict;
use warnings;

use IPC::Open3 qw( open3 );
use Symbol qw( gensym );

my $pid = open3(
   \*STDIN,
   \*STDOUT,
   my $fr_chld_err = gensym(),
   './home/bevs/bin/email'
);

while (<$fr_chld_err>) {
   next if /Module 'eAccelerator' already loaded/;
   print STDERR $_;
}

waitpid($pid, 0)
   or die;

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