#threads

Question

int main()
{
if(fork() == 0)
printf("GATE2018");
if(fork() == 0)
printf("GATE2018");
}

How many times GATE2018 printed?

Comments

3 times ???

assuming each time child process is created succesfully..

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Some good fork() problems

https://gateoverflow.in/76089/operating-system-made-easy-test-series-problem-%23forkproblem

https://gateoverflow.in/63998/fork

Answer 1

int main()
{
if(fork() == 0)
printf("GATE2018");  // a child process is created because fork() == 0

 if(fork() == 0)            // one parent process is created as fork() returns a non zero value, this is process id of previous child process
                                 // another child process is created as fork() == 0
printf("GATE2018");  
}                              // at this point total 3 times GATE 2018 gets printed

Answer 2

whenever the fork()=0  GATE 2018 gets printed.so, total 3 times it is printed

Comments

Just remember here ,

When a child process gets created, process id of the child process which is a +ve value returns to Parent process, and 0 is return to child process,

In this question all child process gets created . But for first fork() call no parent process is created as fork()==0 this condition dis satisfying .

So total 3 process is created , they are :

Child , Parent, and Child hence total 3 times  GATE 2018 gets printed .

Answer 3

When a child process gets created, process id of the child process which is a +ve value returns to Parent process, 0 to child process, and -ve value to parent when child cretaion fails.

When Parent process executes this program:
condition will be FALSE for parent, as fork() will be replaced with +ve process id value.
hence nothing will be printed by parent process.
But newly created child process will print GATE2018 as 'if' evaluates to true for it.

Next Fork() will be executed by Parent and first child process both. here TWO new processes will be created, one by parent and second by the first child. So first child of parent will get its sibling and  first child will get its own child too.

GATE2018 will be printed twice, once by new child and second by child of child

So, in total GATE2018 will be printed thrice! 

Answer 4

Answer (3)

---

if(fork() == 0)   #1
printf("GATE2018");
if(fork() == 0)   #2
printf("GATE2018");

#1)   (2) processes are created .  Half of which enter into "if" . (2/2) = 1.

Therefore 1 time it is printed !

#2)  2 processes created  above come and create (4) processes now!. Half of which enter into "if". (4/2) = 2.

Therefore 2 time it is printed !

Totally (3) times it'll be printed