For the program below, explain what the output will be at Line A. Neglect any sy
ID: 3824536 • Letter: F
Question
For the program below, explain what the output will be at Line A. Neglect any syntax errors you might identify. #include #include #include int main() {int pipefd[2]; pipe(pipefd); int pid = fork(); if (pid == 0){int pipefdC[2]; pipe(pipefdC); int pide = fork(); if (pide == 0){int x = 3*3; write(pipefdC[1], x, sizeof(x)); exit(0);} else {int y; read(pipefdC[0], y, sizeof(y)); y += 4*4; write(pipefd(1], y, sizeof(y)); exit(0);}} else {int z; read(pipefd[0], z, sizeof(z)); z += 5*5; printf("PARENT: value = %d"# z);/* LINE A */exit(0);}}Explanation / Answer
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main()
{
int pipefd[2]; //Declares an array of file descriptors(integers) of size 2.
pipe(pipefd); //Creates a pipe, with the given file descriptors.
int pid = fork(); //Creates a new process, and the id is stored in pid.
if(pid == 0) //For the child process.
{
int pipefdC[2]; //Declares another array of file descriptors of size 2.
pipe(pipefdC); //Creates another pipe, with the given file descriptors.
int pidC = fork(); //Creates another process inside the child, and the proces id stored in pidC.
if(pidC == 0) //For the further child process.
{
int x = 3*3; //x is initialized to 9.
write(pipefdC[1], x, sizeof(x)); //The value 9 is written into the pipe pipefdC.
exit(0); //This child process will come to an end.
}
else //In the parent process(This is still a child to the first parent.)
{
int y;
read(pipefdC[0], y, sizeof(y)); //The variable y will read the value in the pipe.
y += 4*4; //If the child is executed first, the pipefdC will hold 9, and will update y value with y = 9+4*4 = 25.
write(pipefd[1], y, sizeof(y)); //The value 25 is written to another pipe pipefd.
exit(0);
}
}
else //In the parent process.
{
int z;
read(pipefd[0], z, sizeof(z)); //Will read a value from pipe to z. If the child is executed first, it will pipefd will hold 25, and will be read to z.
z += 5*5; //z value is incremented by 25. So, z will become 25 + 25 = 50.
printf("PARENT: value = %d", z); /*LINE A*/ //So, this statement will print the value: 50.
exit(0);
}
}
So, the output could be PARENT: value = 50.
But note that, the code may also lead to indefinite wait, as the parent process may have nothing to read from the pipe, if the parent is executed prior to child.