Question

Write code that forks into two processes: a parent process, and a child process.

Same as the Regular version, except that your code must also be able to handle
negative integers input from the command-line.

If I call your code this way:

    a03 -3 5 -7

The parent process should print out:

Assignment 3
    sum = -5

The sums produced from the test input I use will be in the range [-128 .. 127]

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// Numbers from command line arguments are sent to child process
// from parent process one at a time through pipe.
//
// Child process adds up numbers sent through pipe.
//
// Child process returns sum of numbers to parent process.
//
// Parent process prints sum of numbers.

#include

int main(int argc, char **argv)
{
   // set up pipe

   // call fork()

   if (0 /* replace 0 with test for parent vs child, delete this comment */) {
       // -- running in child process --

       int     sum = 0;

       // Receive numbers from parent process via pipe
       // one at a time, and count them.

       // Return sum of numbers.
       return sum;
       }

   else {
       // -- running in parent process --

       int sum = 0;

       // Send numbers (datatype: int, 4 bytes) from command line arguments
       // starting with argv[1] one at a time through pipe to child process.

       // Wait for child process to return. Reap child process.
       // Receive sum of numbers via the value returned when
       // the child process is reaped.

       printf("sum = %d\n", sum);
       return 0;
       }
}

Answer 1

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/wait.h>

int main(int argc, char *argv[])

{

int fd[2]; //pipe desciptors

pid_t pid; //pid

// create pipe descriptors

pipe(fd);

pid=fork() ; //fork the process

if(pid==0)

{

//child process

int n,a[100],sum=0;

//reading from pipe ,its a blocking process

read(fd[0],&n,sizeof(n)); //reading n from pipe

int i;

for(i=0;i<n;i++) //read n elements from pipe

{

int y;

read(fd[0],&y,sizeof(y)); //read

a[i]=y; //store in array

}

for (i = 0; i < (n); ++i)

{

sum+=a[i]; //calculate the sum

}

write(fd[1],&sum,sizeof(sum)); //send the sum to parent process

exit(0); //exit

}else

{

//parent process

int a[100],sum; //array to hold command line arguments

int i;

//int n=*(argv[1])-'0';

if(argc<2)

{

printf("Enter number of elements and values\n");

return 0;

}

int n=atoi(argv[1]); //read no of elements

//argv[0] stands for program name

for(i=0;i<(n);i++)

{

a[i]=atoi(argv[i+2]); //read each element and store in array

}

write(fd[1],&n, sizeof(n)); //write n

for(i=0;i<n;i++)

{

int x=a[i];

write(fd[1],&x, sizeof(x)); //write n values

}

//wait for child process to return

wait(NULL);

//read sum

read(fd[0],&sum,sizeof(sum));

//print sum

printf("sum = %d \n",sum );

}

}
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