Running Multiple Process

[nebu]

Say i create a c program like



#include <stdlib.h>

int main(){
int i;
for(i=0;i<5;i++)
fork();

//Some code

return 0;
}

how do i make the parent process finish only after all the 5 children have terminated?

[Arndt]

Say i create a c program like



#include <stdlib.h>

int main(){
int i;
for(i=0;i<5;i++)
fork();

//Some code

return 0;
}

how do i make the parent process finish only after all the 5 children have terminated?

You use 'wait' or one of the other functions described on the same manual page.

[nebu]

could u elaborate with some code....

i am not getting very far with the manual pages

[dwhitney67]

It amounts to something as simple as...


man 2 wait


In case you find yourself dazed/confused/deer-in-headlights, here's a basic example...


#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

void childDoSomething();

int main()
{
pid_t chld_pid[5] = {0};
int num_chld = 0;

for (int i = 0; i < 5; ++i)
{
chld_pid[i] = fork();

if (chld_pid[i] == 0)
{
// we are the child; do something very unconstructive
childDoSomething();
exit(0);
}
else if (chld_pid[i] > 0)
{
++num_chld;
}
}

while (num_chld--)
{
sleep(1);
printf("Waiting for children to die...\n");

for (int i = 0; i < 5; ++i)
{
int status;
waitpid(chld_pid[i], &status, 0);
}
}
printf("All children are dead... dead I tell you!\n");

return 0;
}

void childDoSomething()
{
for (int i = 0; i < 5; ++i)
{
sleep(1);
if (i == 0)
printf("The child is running.\n");
else
printf("The child is still running.\n");
}
printf("The child is done.\n");
}

[MindSz]

You can also use threads.

http://www.cs.cf.ac.uk/Dave/C/node32.html