-You should not write to the standard error or output streams from within your
-Perl code, as it is not defined how these are set up. In versions of Exim up to
-at least 4.50, it is possible for the standard output or error to refer to the
-SMTP connection during message reception. Writing to this stream is likely to
-cause chaos. Something may be done about this in later releases.
-
-Unfortunately, the Perl \warn\ statment writes to the standard error stream,
-and this may be embedded in Perl modules that you use, but over which you have
-no control. One way round this is to ensure that the following Perl magic is
-obeyed before \warn\ is used:
-.display asis
-$SIG{__WARN__} = sub { Exim::log_write($_[0]) };
-.endd
-This causes the output of the \warn\ statement to be written to Exim's log
-file.
+.index Perl||standard output and error
+You should not write to the standard error or output streams from within your
+Perl code, as it is not defined how these are set up. In versions of Exim
+before 4.50, it is possible for the standard output or error to refer to the
+SMTP connection during message reception via the daemon. Writing to this stream
+is certain to cause chaos. From Exim 4.50 onwards, the standard output and
+error streams are connected to \(/dev/null)\ in the daemon. The chaos is
+avoided, but the output is lost.
+
+.index Perl||\warn\, use of
+The Perl \warn\ statement writes to the standard error stream by default. Calls
+to \warn\ may be embedded in Perl modules that you use, but over which you have
+no control. When Exim starts up the Perl interpreter, it arranges for output
+from the \warn\ statement to be written to the Exim main log. You can change
+this by including appropriate Perl magic somewhere in your Perl code. For
+example, to discard \warn\ output completely, you need this:
+.display asis
+$SIG{__WARN__} = sub { };
+.endd
+Whenever a \warn\ is obeyed, the anonymous subroutine is called. In this
+example, the code for the subroutine is empty, so it does nothing, but you can
+include any Perl code that you like. The text of the \warn\ message is passed
+as the first subroutine argument.
git://git.exim.org / exim.git / blobdiff