Re: wait_for_file ?? [GL2PS error: Bad file pointer]

[Michael D Godfrey]

On 09/13/2010 03:54 PM, Ben Abbott wrote:

However, I did find an approach that eliminates all errors with pipes. I don't understand why this works for gl2ps, but when I add *both* the waitpid() and pclose(pid), then I get no errors.

	pid = popen ("cat > test.eps", "w");
	drawnow ("eps" , sprintf ("%d" , pid));
	waitpid (pid);
	pclose (pid);

I have a few more changes to make to the printing  routines. With some luck I'll post another proposed changeset this evening.

Ben

This is very weird.  waitpid(pid)  waits on a change of state of a process
id, not a file or pipe descriptor.  Also, the pid passed to drawnow() is, according
to Shai, passed by value.   But, it is possible that something that waitpid looks
at in the pipe descriptor does change and that makes it work.   Is there any one
who knows if this should really work?

It would be useful to time how long the waitpid actually waits.  If it waits for some
time then it is definitely seeing a change in the descriptor pointed to by pid.

The pclose() is definitely needed.

Michael