Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!sdd.hp.com!hplabs!hpcc05!hpsciz!dougy
From: dougy@hpsciz.sc.hp.com (Doug Yip)
Newsgroups: comp.unix.questions
Subject: Re: A question about read() system call!!
Message-ID: <690002@hpsciz.sc.hp.com>
Date: 22 May 91 21:52:13 GMT
References: <28398698.26968@maccs.dcss.mcmaster.ca>
Organization: Hewlett-Packard, Santa Clara, CA
Lines: 22


>  I wonder if I can get help regarding the unix system call "read()".
>When a program executes this system call to read from an empty pipeline,  
>shouldn't it return zero ( nothing is read ) and passes control to the next 
>statement? I think it remains stuck waiting for something to be put it the 
>pipeline. How can I overcome this behaviour? That is making it pass control 
>to next statement even if pipeline is empty. I would appreciate responses.

   
There are two options to solve this problem:

If the file is already open, you can do a fcntl(fd,F_SETFL,O_NDELAY).

If the file is not open yet, you can specify the O_NDELAY option when you
open the file.

You need to include the following files for the options to work according
to my manual:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>