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Clean up "premature end of headers" FAQ and add additional

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(and more common) cause description.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@78298 13f79535-47bb-0310-9956-ffa450edef68
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Ken Coar
1997-06-12 15:24:00 +00:00
parent e89e7d53c1
commit f21eb24f00
1 changed files with 33 additions and 12 deletions
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docs/manual/misc/FAQ.html
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@@ -15,7 +15,7 @@
<!--#include virtual="header.html" --> <!--#include virtual="header.html" -->
<H1 ALIGN="CENTER">Apache Server Frequently Asked Questions</H1> <H1 ALIGN="CENTER">Apache Server Frequently Asked Questions</H1>
<P> <P>
$Revision: 1.70 $ ($Date: 1997/06/12 11:29:11 $) $Revision: 1.71 $ ($Date: 1997/06/12 15:24:00 $)
</P> </P>
<P> <P>
The latest version of this FAQ is always available from the main The latest version of this FAQ is always available from the main
@@ -569,27 +569,48 @@
<P> <P>
It means just what it says: the server was expecting a complete set of It means just what it says: the server was expecting a complete set of
HTTP headers (one or more followed by a blank line), and didn't get HTTP headers (one or more followed by a blank line), and didn't get
them. The most common cause of this (aside from people not them.
outputting the required headers at all) a result of an interaction </P>
with perl's output buffering. To make perl flush its buffers <P>
after each output statement, insert the following statements before your The most common cause of this problem is the script dying before
first <CODE>print</CODE> or <CODE>write</CODE> statement: sending the complete set of headers, or possibly any at all, to the
server. To see if this is the case, try running the script standalone
from an interactive session, rather than as a script under the server.
If you get error messages, this is almost certainly the cause of the
&quot;premature end of script headers&quot; message.
</P>
<P>
The second most common cause of this (aside from people not
outputting the required headers at all) is a result of an interaction
with Perl's output buffering. To make Perl flush its buffers
after each output statement, insert the following statements around
the <CODE>print</CODE> or <CODE>write</CODE> statements that send your
HTTP headers:
</P> </P>
<P> <P>
<DL> <DL>
<DD><CODE>$cfh = select (STDOUT);<BR> <DD><CODE>{<BR>
$| = 1;<BR> &nbsp;local ($oldbar) = $|;<BR>
select ($cfh);</CODE> &nbsp;$cfh = select (STDOUT);<BR>
&nbsp;$| = 1;<BR>
&nbsp;#<BR>
&nbsp;# print your HTTP headers here<BR>
&nbsp;#<BR>
&nbsp;$| = $oldbar;<BR>
&nbsp;select ($cfh);<BR>
}</CODE>
</DD> </DD>
</DL> </DL>
</P> </P>
<P> <P>
This is generally only necessary when you are calling external This is generally only necessary when you are calling external
programs from your script that send output to stdout, or if there will programs from your script that send output to stdout, or if there will
be along delay between the time the headers are sent and the actual be a long delay between the time the headers are sent and the actual
content starts being emitted. To maximise performance, you should content starts being emitted. To maximise performance, you should
turn buffering back <EM>on</EM> (with <CODE>$| = 0</CODE> or the turn buffer-flushing back <EM>off</EM> (with <CODE>$| = 0</CODE> or the
equivalent) after the statements that send the headers. equivalent) after the statements that send the headers, as displayed
above.
</P>
<P> <P>
If your script isn't written in Perl, do the equivalent thing for If your script isn't written in Perl, do the equivalent thing for
whatever language you <EM>are</EM> using (<EM>e.g.</EM>, for C, call whatever language you <EM>are</EM> using (<EM>e.g.</EM>, for C, call