fork

Question

#include <stdio.h>
#include <unistd.h>
int main() {
    int i;
    for(i=1;i<=3;i++) {
        fork();
        printf("*");
    }
    return 0;
}

how many times * will be printed ?...is it 11?

Comments

total process created is 8

and total *printed =14

Answer 1

The above program is same as 

  fork();

  printf("*");

  fork();

  printf("*");

  fork();

printf("*");

; 

 1st fork at root, 2nd fork at level 1,3rd fork at level2

 14 is the ans.

But answer can be more than 14, due to printf buffer also being copied as a result of fork.

Comments

if we interchange the fork and print statement given below then 

1. #include <stdio.h>
2. #include <unistd.h>
3. int main() {
4. int i;
5. for(i=1;i<=3;i++) {
6. printf("*");
7. fork();
8. }
9. return 0;
10. }

---

seven

---

to @yash patidar, as per your modification, we will get the sequence 

printf  ← only 1 process here thus 1 time print

fork  ← creates 2^1 = 2 processes including parent

printf  ← 2 processes here, thus 2 times print

fork ← creates 2^2=4 processes

printf ← 4 processes here, thus 4 times print

fork ← creates 2^3=8 processes
now, return statement is encountered for all processes created

thus in total 1+2+4 = 7 times * will be printed

Answer 2

Here fork() is called 3 times through the loop from i=1 to 3 . each time * gets printed .

So, total number of process created :

(2¹ - 1 ) + 1 =1 + 1 = 2  .. at first level 

( 2² - 1) + 1 = 3+1 = 4 ... at 2nd level

(2³-1)+1 =7 + 1 = 8 ...  at 3rd level

so total process created 2+4+8 = 14 

Comments

Same type of question is asked by different gate overflow users so many times.

So many users are given their solutions, but this is the correct explanation which clears doubt.

Answer 3

By using the formula Total processesd will be created will be 2ⁿ

first fork will create 2 processes so 2-"*"

By the second fork there will be 4 processes so 4-"*"

So for the three forks total processes will be created will be 8 so 8 "*"

Total 8+4+2=14 is the answer

Comments

7 child processs are created.and 14 times * will be printed .

---

Check this way :

Here fork() is called 3 times through the loop from i=1 to 3 . each time * gets printed .

(2¹ - 1 ) + 1 =1 + 1 = 2  .. at first level 

( 2² - 1) + 1 = 3+1 = 4 ... at 2nd level

(2³-1)+1 =7 + 1 = 8 ...  at 3rd level

so total process created 2+4+8 = 14 

Answer 4

The answer would be 14