pen@lysator.liu.se (Peter Eriksson) (10/18/90)
I'm experiencing some strange things with the code segment below. I have to
add the call to usleep() (or use semaphore signalling from the child to the
parent) in order to have the 'fd' available in the child. Apparently something
goes wrong if I close it too fast in the parent. I just don't understand why
this is so. Any suggestions?
fd = accept(...);
if (fork())
{
/* usleep(100000); */
close(fd);
return;
}
dup2(fd, 0);
execl(...);
And, is there any portable way to code a wait in the parent to be sure
that the child has begun executing? (I'm using SysV semaphores right now,
which works real nice, but how common are those? How many versions of
Unix has those in the kernel "by default"?)
--
Peter Eriksson pen@lysator.liu.se
Lysator Computer Club ...!uunet!lysator.liu.se!pen
University of Linkoping, Sweden "Seize the day!"dkeisen@Gang-of-Four.Stanford.EDU (Dave Eisen) (10/25/90)
In article <364@lysator.liu.se> pen@lysator.liu.se (Peter Eriksson) writes: > > >And, is there any portable way to code a wait in the parent to be sure >that the child has begun executing? Not the world's most efficient solution, but you can open a pipe before you fork, close both ends in the child, close the write end in the parent and then read one byte from the read end. The parent will sleep in the read until the child closes the write end of the pipe. -- Dave Eisen Home: (415) 323-9757 dkeisen@Gang-of-Four.Stanford.EDU Office: (415) 967-5644 1447 N. Shoreline Blvd. Mountain View, CA 94043