Description
Write a C program to implement process System calls ? [Hint use fork())]
- How many processes are created in a given program?
#include <stdio.h> #include <unistd.h> int main()
{ int i; for (i = 0; i < 4; i++) fork(); return 0;
}
- When will line J be reached?
#include <sys/types.h>
#include <stdio.h> #include <unistd.h> int main()
{ pid_t pid;
/* fork a child process */ pid = fork(); if (pid < 0) { /* error occurred */ fprintf(stderr, “Fork Failed”); return 1;
} else if (pid == 0) { /* child process */ execlp(“/bin/ls”,”ls”,NULL); printf(“LINE J”);
} else { /* parent process */
/* parent will wait for the child to complete */ wait(NULL); printf(“Child Complete”);
} return 0;
}
- What are the pid values?
#include <sys/types.h>
#include <stdio.h> #include <unistd.h> int main()
{ pid_t pid, pid1; /* fork a child process */ pid = fork(); if (pid < 0) { /* error occurred */ fprintf(stderr, “Fork Failed”); return 1;
} else if (pid == 0) { /* child process */ pid1 = getpid(); printf(“child: pid = %d”,pid); /* A */ printf(“child: pid1 = %d”,pid1); /* B */
} else { /* parent process */ pid1 = getpid(); printf(“parent: pid = %d”,pid); /* C */ printf(“parent: pid1 = %d”,pid1); /* D */ wait(NULL);
} return 0;
}
- What will be at Line X and Line Y?
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h> #define SIZE 5 int nums[SIZE] = {0,1,2,3,4}; int main()
{ int i; pid t pid; pid = fork(); if (pid == 0) { for (i = 0; i < SIZE; i++) { nums[i] *= -i; printf(“CHILD: %d “,nums[i]); /* LINE X */ } } else if (pid > 0) { wait(NULL);
for (i = 0; i < SIZE; i++) printf(“PARENT: %d “,nums[i]); /* LINE Y */
} return 0;
}
