n3jqJskF

1//Note: pipes are not bi-directional, so you will need two pipes per process, one for receiving (reading) and one for sending (writing).  if you the to send (write) something using pipe1 you need to close the reading end of that pipe, namely close(pipe1[0]).  In the same way, if you need to receive something from the someone, you have to use another pipe, let say pipe2, so you use the reading end part and close the writing end, namely close(pipe2[1]) */
2
3//Sorry for any typo, I hope that this code will help you to beeter understand, how to use the API for process. Feel free to extend this code for two and three childrens.  
4
5#include <stdlib.h>
6#include <stdio.h>
7#include <unistd.h>
8#include <sys/types.h>
9
10int main(int argv, char** argc) {
11    // initialize pipes
12    int p1[2];
13    int p2[2];
14    pipe(p1);
15    pipe(p2);
16    int luis;
17
18    int numElements = 6; //num of elements in the array
19    luis = fork();  //creating a child
20
21    if (luis == 0) { // If I am the child read the elements of the array that my parent sent me
22        
23        close(p1[1]); //closing the writing end of pipe1 (p1), I am using p1 for reading so p1[0] is open for reading from my parent
24        close(p2[0]); //closing the  reading end of pipe2 (p2), I am using p2 for sending (writing) the sumation to my parent 
25        int vals[numElements];
26        read(p1[0], &vals, sizeof(vals));
27
28        // compute the sum
29        int sum = 0;
30        printf("child %d: received ", getpid()); //printing my pid and the array that I just received from my parent
31        int i;
32        for (i=0;i<numElements;i++){   
33            printf("%d, ", vals[i]);
34            sum += vals[i];    //Adding the elments of the array
35        }
36        printf("\n");   
37        printf("child %d: sending %d to parent\n", getpid(), sum); 
38        // send result to parent
39        write(p2[1], &sum, sizeof(sum)); //sending to the parent the sum of the array
40        exit(0);     //key line of code.
41    } else {
42        // parent
43        close(p1[0]);  //closing reading, because I will use pipe1 for sending info to my child
44        close(p2[1]);  //closing writing, bacuase I will use this pipe2 for receiving the summation from my child 
45        // send values to child
46        int valsToSend[6] = {2,3,7,-1,10,6};
47        write(p1[1], &valsToSend, sizeof(valsToSend));
48        printf("parent is %d\n", getpid());
49        // receive and print the final value
50        int recval;
51        read(p2[0], &recval, sizeof(recval));
52        printf("parent: final sum is %d\n", recval);
53        exit(0);
54    }
55    return 0;
56}