Why IPC::Run3 cannot capture any standard output in Apache environment?

Question

%use IPC::Run3;
%my $a;
%run3 ['echo','hello'],\undef,\$a;
<% $a %>

Above mason code works very well when I use Mason from a standalone script, as descriped in HTML::Mason::Admin. Unfortunately, when running with perl_mode, $a is an empty string. Below is my httpd.conf

 Alias /mason_book /home/charlse/f/books/mason_book
 <Location /mason_book>
    SetHandler perl-script
    AddHandler perl-script .mas
    PerlHandler HTML::Mason::ApacheHandler
    PerlAddVar  MasonCompRoot  "mason_book => /home/charles/f/books/mason_book"
 </Location>
 <Directory "/home/chunywan/f/books/mason_book">
    Options Indexes FollowSymLinks
    AllowOverride None
    Order allow,deny
    Allow from all
 </Directory>

BTW

 %use IPC::Run qw(run timeout);
 %my @cmd=qw(echo hello world);
 %my ($in,$out,$err);
 %run(\@cmd, \$in, \$out, \$err) or die "cat: $?";
 <pre>
   out <% $out %>
 </pre>

I just try IPC::Run which works very well in both standalone mode and mod_perl mode. It seems that I have to update all my source code to use IPC::Run instead of IPC::Run3.

Answer 1

I believe the solution is to temporarily re-open STDIN/STDOUT, and then close it after your command finishes.

use IPC::Run3;
my $a;

#save off existing stdin/out
my ($save_stdin,$save_stdout);
open $save_stdin, '>&STDIN';
open $save_stdout, '>&STDOUT';

#open it again as the "normal things"
open STDIN, '>&=0';
open STDOUT, '>&=1';
run3 ['echo','hello'],\undef,\$a;

#clean up after yourself
close(STDIN);
close(STDOUT);
open STDIN, '>&', $save_stdin;
open STDOUT, '>&', $save_stdout;

I ran into the same issue with IPC::Open3 and solved it here: https://stackoverflow.com/a/24311232/312208