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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
void child( int seconds );
int children = 15;
int main(void)
{
printf("Parent ID %d, Main ID %d \n", getppid(), getpid());
for(int i=0;i<children;i++)
{
if(fork()==0)
{
child(children-i); // pass seconds to sleep
}
else
{
wait(NULL);
}
}
}
void child(int seconds)
{
printf("Parent ID %d, Child ID %d, Sleeping %d seconds.\n", getppid(), getpid(), seconds);
sleep(seconds);
exit(0);
}
[acool@localhost C-Exercises]$ date
Sun Oct 23 04:14:24 PM PDT 2022
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ gcc parent_children.c
[acool@localhost C-Exercises]$ ./a.out
Parent ID 4298, Main ID 10357
Parent ID 10357, Child ID 10358, Sleeping 15 seconds.
Parent ID 10357, Child ID 10394, Sleeping 14 seconds.
Parent ID 10357, Child ID 10436, Sleeping 13 seconds.
Parent ID 10357, Child ID 10475, Sleeping 12 seconds.
Parent ID 10357, Child ID 10510, Sleeping 11 seconds.
Parent ID 10357, Child ID 10532, Sleeping 10 seconds.
Parent ID 10357, Child ID 10546, Sleeping 9 seconds.
Parent ID 10357, Child ID 10558, Sleeping 8 seconds.
Parent ID 10357, Child ID 10581, Sleeping 7 seconds.
Parent ID 10357, Child ID 10598, Sleeping 6 seconds.
Parent ID 10357, Child ID 10607, Sleeping 5 seconds.
Parent ID 10357, Child ID 10613, Sleeping 4 seconds.
Parent ID 10357, Child ID 10647, Sleeping 3 seconds.
Parent ID 10357, Child ID 10732, Sleeping 2 seconds.
Parent ID 10357, Child ID 10815, Sleeping 1 seconds.
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ ps -A |grep a.out
10357 pts/0 00:00:00 a.out
10394 pts/0 00:00:00 a.out
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ pstree -p 10357
a.out(10357)───a.out(10436)
[acool@localhost C-Exercises]$
Slightly different version, in this version we don't wait() for each child individually.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
void child( int seconds );
int children = 15;
int main(void)
{
printf("Parent ID %d, Main ID %d \n", getppid(), getpid());
for(int i=0;i<children;i++)
{
if(fork()==0)
{
child(children-i); // pass seconds to sleep
}
}
while (wait(NULL) > 0); // wait for all children to finish
}
void child(int seconds)
{
printf("Parent ID %d, Child ID %d, Sleeping %d seconds.\n", getppid(), getpid(), seconds);
sleep(seconds);
exit(0);
}
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ gcc parent_children.c
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ ./a.out
Parent ID 4298, Main ID 14322
Parent ID 14322, Child ID 14323, Sleeping 15 seconds.
Parent ID 14322, Child ID 14324, Sleeping 14 seconds.
Parent ID 14322, Child ID 14325, Sleeping 13 seconds.
Parent ID 14322, Child ID 14326, Sleeping 12 seconds.
Parent ID 14322, Child ID 14327, Sleeping 11 seconds.
Parent ID 14322, Child ID 14328, Sleeping 10 seconds.
Parent ID 14322, Child ID 14329, Sleeping 9 seconds.
Parent ID 14322, Child ID 14330, Sleeping 8 seconds.
Parent ID 14322, Child ID 14331, Sleeping 7 seconds.
Parent ID 14322, Child ID 14332, Sleeping 6 seconds.
Parent ID 14322, Child ID 14333, Sleeping 5 seconds.
Parent ID 14322, Child ID 14334, Sleeping 4 seconds.
Parent ID 14322, Child ID 14335, Sleeping 3 seconds.
Parent ID 14322, Child ID 14336, Sleeping 2 seconds.
Parent ID 14322, Child ID 14337, Sleeping 1 seconds.
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ pstree -p 14322
a.out(14322)─┬─a.out(14323)
├─a.out(14324)
├─a.out(14325)
├─a.out(14326)
├─a.out(14327)
├─a.out(14328)
├─a.out(14329)
├─a.out(14330)
├─a.out(14331)
├─a.out(14332)
├─a.out(14333)
├─a.out(14334)
└─a.out(14335)
[acool@localhost C-Exercises]$ ps -A |grep a.out
14322 pts/0 00:00:00 a.out
14323 pts/0 00:00:00 a.out
14324 pts/0 00:00:00 a.out
14325 pts/0 00:00:00 a.out
14326 pts/0 00:00:00 a.out
14327 pts/0 00:00:00 a.out
14328 pts/0 00:00:00 a.out
14329 pts/0 00:00:00 a.out
14330 pts/0 00:00:00 a.out
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ pstree -p 14322
a.out(14322)─┬─a.out(14323)
├─a.out(14324)
├─a.out(14325)
├─a.out(14326)
├─a.out(14327)
└─a.out(14328)
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$
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