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<faq metafile="error.xml.meta">
<parentdocument href="./">FAQ</parentdocument>

<title>Error Messages - Frequently Asked Questions</title>
<description>What does this error message mean?</description>



<section id="error"><title>Error Messages</title>
    <ul>
    <li><a href="#error.sendfile">Invalid argument:
    core_output_filter: writing data to the network</a></li>
    <li><a href="#error.acceptex">AcceptEx failed</a></li>
    <li><a href="#error.scriptheaders">Premature end of script 
    headers</a></li>
    </ul>

    <section id="error.sendfile"><title>Invalid argument:
    core_output_filter: writing data to the network</title>

    <p>Apache uses the <code>sendfile</code> syscall on platforms
    where it is available in order to speed sending of responses.
    Unfortunately, on some systems, Apache will detect the presence of
    <code>sendfile</code> at compile-time, even when it does not work
    properly.  This happens most frequently when using network or
    other non-standard file-system.</p>

    <p>Symptoms of this problem include the above message in the error
    log and zero-length responses to non-zero-sized files.  The
    problem generally occurs only for static files, since dynamic
    content usually does not make use of <code>sendfile</code>.</p>

    <p>To fix this problem, simply use the <directive
    module="core">EnableSendfile</directive> directive to disable
    <code>sendfile</code> for all or part of your server.  Also see
    the <directive module="core">EnableMMAP</directive>, which can
    help with similar problems.</p>

    </section>

    <section id="error.acceptex"><title>AcceptEx Failed</title>

    <p>If you get error messages related to the <code>AcceptEx</code> syscall
    on win32, see the <directive module="mpm_winnt">Win32DisableAcceptEx</directive>
    directive.</p>
    </section>


    <section id="error.scriptheaders"><title>Premature end of script 
    headers</title>

    <p>Most problems with CGI scripts result in this message written in the
    error log together with an <code>Internal Server Error</code> delivered
    to the browser.  A guide to helping debug this type of problem is
    available in the <a href="../howto/cgi.html#troubleshoot">CGI
    tutorial</a>.</p>
    </section>

</section>

</faq>

