fork() system call.

Question

for ( i = 1; i<=3; i++ )

{

   fork();

   fork();

}

How many child process will create ?

Answer 1

Before going to this question, let analyze

for(i=1;i<=3;i++)

{

       fork();

}

it is equivalent to 

1.fork();

2.fork();

3.fork();

using fork() system call we create one more process ===> double the no.of processes

before the 1st line ===> totally you have 1 process

after the first line  ===> totally you have 2 processes

after the second line  ===> totally you have 4 processes

after the third line  ===> totally you have 8 processes ===> total = 2ⁿ processes

in this 8 process, 1 parent process, 3 intermediate processes , and 4 leave processes

Child processes = 3+4 = 7 ( note that every intermediate process is a child process for some process ) = 2ⁿ-1 processes

 

coming to your original question,

for(i=1;i<=3;i++)

{

       fork();
       fork();

}

it is equivalent to 

1.fork();

  fork();

2.fork();

  fork();

3.fork();

  fork();

 

it is equivalent to, let m=2n

for(i=1;i<=m;i++)

{

      fork();

}

===> child processes = 2^m-1 =  2²ⁿ-1 =  2⁶-1 = 63

Comments

good one :p

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thank you for your great explanation.

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what a beautiful explanation

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It should be best answer :3

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@shaikh bro thnxx for this explanation :)

for first time i understood fork

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So,We used the formula  2^(n-1) to calculate the child process but 

What are the no.of parent processes in the above Question?

Do we need to count only the first Parent process from where all the child processes started??

or

Do we need to count every process where there’s a fork and starts a new child process?