Unblocking filedescriptor(s)

[Stefan Krabbe]

Hi there,
I am programming in a 4.3BSD environment. And I have a problem
I hope that somebody here can help me with. 
 In a program I am currently writing I make a filedescriptor unblocking
this way:
             fcntl(filedescriptor, F_SETFL, FNDELAY);
.. and it works just fine. But what do I do if I want it make it block-
ing again ? I have noticed that if I from within my program do
             system( ... );
 -then all my previously un-blocking filedescriptors become blocking 
again !?! If you know how to make an un-blocking filedescriptor
blocking again, then please mail me.

Best Regards
            Stefan
                                     ___
  Name:  Stefan Krabbe       .......(o o).......
  Email: cthulhu at diku.dk     ---vvv---U---vvv---
  Institute of Computer Science, University of Copenhagen.