fork() in C

fork() in C

·       

    Fork system call use for creates a new process, which is called child process.

·      This child process runs concurrently with Parent process (The Process from which fork() is called).

·      After a new child process created, both processes will execute the next instruction following the fork() system call.

·      A child process use same PC(program counter), same CPU registers, same open files which use in parent process.

Argument: 0

Return Value:

Negative Value: Creation of a child process was unsuccessful.
Zero:                   Returned to the newly created child process.
Positive value:    Returned to parent or caller. The value contains process ID of newly created child process.

1. Predict the Output of the following program. 

#include<stdio.h> #include<sys/types.h> #include<unistd.h> int main() {     // make two process which run same     // program after this instruction     fork();     printf("Hello world!\n");     return 0; }

Output:

Hello world!

Hello world! 

2. Calculate number of times hello is printed.

#include  <stdio.h> #include  <sys/types.h> int main() {     fork();     fork();     fork();     printf("hello\n");     return 0; }

Output:

hello

hello

hello

hello

hello

hello

hello

hello

Number of times hello printed is equal to number of process created. Total Number of Processes = 2ⁿ where n is number of fork system calls. So here n = 3, 2³ = 8