Which log are you looking in. Use of printf() at C level would only go to
main Apache error log and never to a virtual host error log.

Graham


On 4 December 2012 17:46, Linux Omicron <[email protected]> wrote:

> Thanks for reply Graham.
> I did try with fflush() in the c library code but no change in output. The
> log file shows only python print statement but c printf() have been
> discarded.
>
> Thanks,
> Linux Omicron.
>
> On Tuesday, October 2, 2012 3:17:42 PM UTC+9, Graham Dumpleton wrote:
>
>> On 23 September 2012 21:27, Linux Omicron <[email protected]> wrote:
>> > Hello Everyone,
>> >
>> > I am developing a web application using pylons pyramid. I am not using
>> > default web server waitress but relying on mod_wsgi.
>> > My pyramid application internally uses a c library. In the c library,
>> some
>> > places,printf() statement is used for debug logs.
>> > When I run my pyramid application under mode_wsgi, I observed that
>> debug
>> > information was being logged in application log file for python print
>> > statements but none of the printf() were logged.
>> > Don't print and printf() have same function to print on stdout?
>> > How do I enable logging using printf() statement?
>>
>> The issue in this case is going to be how Apache attaches C
>> stdout/stderr to the Apache error log. The way it is done means it is
>> effectively buffered. This means that if there is no explicit fflush()
>> done in the C code to force writing out the messages to the Apache
>> error log, they will only get flushed when the buffer fills up, or if
>> you are lucky when the process exits and stdout/stderr are
>> automatically flushed on closure.
>>
>> Also be aware that being C level stdio/stderr I/O operations, when the
>> messages appear in the Apache error log they will not be prefixed with
>> any timestamp information.
>>
>> Graham
>>
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