On 08/31/2012 12:21 PM, David F. Skoll wrote:
On Fri, 31 Aug 2012 10:54:00 +0900
Nathan Findley <nat...@zenlok.com> wrote:
From our more knowledgeable mimedefang users, I would appreciate an
explanation about what is happening in the mimedefang.pl
"resend_message_specifying_mode" method. The child execs sendmail.
The message data is sitting in the child process's STDIN, correct?
Nope. The real magic happens here:
$pid = open(CHILD, "|-");
This forks a process and connects STDIN of the child process to the
CHILD descriptor in the parent.
{ exec($sm, @cmd); } <-- how is sendmail receiving the contents of
the message? I don't see any explicit piping happening.
Whatever the parent process writes to the CHILD descriptor shows up on
STDIN of the child. As in:
if ($pid) { # In the parent -- pipe mail message to the child
print CHILD $body;
close(CHILD);
return;
}
And you can stream messages in filter_end if you like.
When CHILD calls exec how is it that sendmail able to find the message
data on STDIN? Does calling exec always pass any existing STDIN data to
the executed command? It seems to me that this is what is happening. I
simply had no idea that if a parent process (CHILD in this case) has
data in STDIN and then calls exec the STDIN data will be passed to the
program being called (sendmail in this case).
Thanks,
Nate
--
システムマネージャー/開発責任者
Zenlok株式会社
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