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Top Forums Programming fwrite takes extremely long time Post 77163 by jim mcnamara on Tuesday 5th of July 2005 09:58:02 AM
Old 07-05-2005
You may want to consider POSIX aio - asynchronous I/O. Try man aio. e.g., aio_write, aio_read

aio allows you to request an i/o operation, then do soemthing else in your code. When you are done with the 'something else' you go back and query the completion status. You are trying to do real time processing.

You really should consider a design change. Create two processes - one to get/read the data, then send it to shared memory, and a second process which just does file writing using the shared memory data.
 

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FREAD(3)						     Linux Programmer's Manual							  FREAD(3)

NAME
fread, fwrite - binary stream input/output SYNOPSIS
#include <stdio.h> size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream); size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream); DESCRIPTION
The function fread reads nmemb elements of data, each size bytes long, from the stream pointed to by stream, storing them at the location given by ptr. The function fwrite writes nmemb elements of data, each size bytes long, to the stream pointed to by stream, obtaining them from the loca- tion given by ptr. For non-locking counterparts, see unlocked_stdio(3). RETURN VALUE
fread and fwrite return the number of items successfully read or written (i.e., not the number of characters). If an error occurs, or the end-of-file is reached, the return value is a short item count (or zero). fread does not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred. CONFORMING TO
The functions fread and fwrite conform to ANSI X3.159-1989 (``ANSI C''). SEE ALSO
read(2), write(2), feof(3), ferror(3), unlocked_stdio(3) BSD MANPAGE
1996-05-17 FREAD(3)
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