test_fork.c

#include <stdio.h>
#include <string.h>
#include <sys/types.h>

#define MAX_COUNT 200
#define BUF_SIZE 100

void ChildProcess(char [], char []); /* child process prototype */

void main(void)
{
pid_t pid1, pid2, pid;
int status;
int i;
char buf[BUF_SIZE];

printf("*** Parent is about to fork process 1 ***\n");
if ((pid1 = fork()) < 0) {
printf("Failed to fork process 1\n");
exit(1);
}
else if (pid1 == 0)
ChildProcess("First", " ");

printf("*** Parent is about to fork process 2 ***\n");
if ((pid2 = fork()) < 0) {
printf("Failed to fork process 2\n");
exit(1);
}
else if (pid2 == 0)
ChildProcess("Second", " ");

sprintf(buf, "*** Parent enters waiting status .....\n");
write(1, buf, strlen(buf));
pid = wait(&status);
sprintf(buf, "*** Parent detects process %d was done ***\n", pid);
write(1, buf, strlen(buf));
pid = wait(&status);
printf("*** Parent detects process %d is done ***\n", pid);
printf("*** Parent exits ***\n");
exit(0);
}

void ChildProcess(char *number, char *space)
{
pid_t pid;
int i;
char buf[BUF_SIZE];

pid = getpid();
sprintf(buf, "%s%s child process starts (pid = %d)\n",
space, number, pid);
write(1, buf, strlen(buf));
for (i = 1; i <= MAX_COUNT; i++) {
sprintf(buf, "%s%s child's output, value = %d\n", space, number, i);
write(1, buf, strlen(buf));
}
sprintf(buf, "%s%s child (pid = %d) is about to exit\n",
space, number, pid);
write(1, buf, strlen(buf));
exit(0);
}