On 07/13/2014 04:53 PM, Paul LaFollette wrote:
Kind people,
I have thrown together a little C/UNIX program that forks a child
process, then proceeds to let the child and parent alternate. Either
can run until it pauses itself and wakes the other.
I would like to know if there be a way to create the same behavior in
Python 3, preferably in a non-platform dependent fashion. I would
prefer to use processes rather than threads, but could live with
threads if I had to. I've studied the documentation for the
multiprocessing and thread modules, but I can't see an easy way to do
what I want to do. I need minimal communication between processes
beyond what i have described, so creating queues or pipes seems like
overkill. Unlike what I have written here, I will want to exec the
child rather than write the whole thing in the else clause. Is there
a reasonably simple way to do this? A reference to useful
documentation would be appreciated. Sample code even more so, of course.
Thank you
Paul
There is a quite reasonable way to do what you want, but that involves
the multiprocessing and queue modules, both of which you have eliminated
from consideration.
So you have to ask yourself: What do you gain from using Python if you
eliminate all the tools Python provides?
Gary Herron
-------------------------
Paul S. LaFollette, Jr
CIS Department
Temple University
+1 215 204 6822
paul.lafolle...@temple.edu <mailto:paul.lafolle...@temple.edu>
http://knight.cis.temple.edu/~lafollet
<http://knight.cis.temple.edu/%7Elafollet>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <errno.h>
int main(int argc, char **argv)
{
void handler(int);
pid_t pid;
signal(SIGCONT, handler);
pid = fork();
if (pid < 0) //failure
{
printf("Unable to fork\n");
exit(1);
}
else if (pid > 0) // parent
{
while (1)
{
printf("Parent waiting for child to do something\n");
pause();
printf("Parent doing nifty stuff.\n");
sleep(1);
printf("Parent waking child\n");
errno = 0;
if (kill(pid, SIGCONT) < 0)
perror("Parent failed to SIGCONT child.");
}
}
else //pid == 0 so child
{
while (1)
{
printf (" Child doing useful
work.\n");
sleep(1);
printf(" Child waking
parent\n");
if (kill(getppid(), SIGCONT) < 0)
perror("Child failed to SIGCONT parent.");
printf(" Child waiting for
parent to do something\n");
pause();
}
}
}
void handler(int signum)
{
}
===============================================================================
Output:
Parent waiting for child to do something
Child doing useful work.
Child waking parent
Child waiting for parent to do
something
Parent doing nifty stuff.
Parent waking child
Parent waiting for child to do something
Child doing useful work.
Child waking parent
Child waiting for parent to do
something
Parent doing nifty stuff.
Parent waking child
Parent waiting for child to do something
Child doing useful work.
Child waking parent
Child waiting for parent to do
something
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