05.c

/**
 *  @author Rajendra Kumar Yadav
 * @date Feb 19 2020
 * */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
/**
 * Step 1 − Create pipe1 for the parent process to write and the child process
 * to read.
 * Step 2 − Create pipe2 for the child process to write and the parent process
 * to read.
 * Step 3 − Close the unwanted ends of the pipe from the parent and child side.
 * Step 4 − Parent process to write a message and child process to read and
 * display on the screen. Step 5 − Child process to write a message and parent
 * process to read and display on the screen.
 * */
int main(int argc, char **argv)
{
    int pipefds1[2], pipefds2[2];
    int pid;

    char pipe1writemessage[20] = "Hi";
    char pipe2writemessage[20] = "Hello";

    char readmessage[20];

    if ((pipe(pipefds1)) == -1) {
        printf("Unable to create pipe 1 \n");
        perror("Error ");
        return 1;
    }

    if ((pipe(pipefds2)) == -1) {
        printf("Unable to create pipe 2 \n");
        perror("Error ");
        return 1;
    }
    pid = fork();
    /*************************************
     *    if pid == 0                     *
     *        It is Child                 *
     *    else                            *
     *        Parent;                     *
     * ***********************************/

    if (pid != 0) {
        close(pipefds1[0]);  // closing pipe1 read end
        close(pipefds2[1]);  // closing pipe2 write end

        printf("In Parent: Writing to pipe 1 – Message is %s\n", pipe1writemessage);

        /************************************
         * Writing into pipe1 from child   *
         * *********************************/
        if (write(pipefds1[1], pipe1writemessage, sizeof(pipe1writemessage)) == -1)
            perror("Error ");

        /************************************
         * Writing into pipe2 from parent   *
         * *********************************/
        if ((read(pipefds2[0], readmessage, sizeof(readmessage))) != -1) {
            printf("In Parent: Reading from pipe 2 – Message is %s\n", readmessage);
        }
    }
    else {
        close(pipefds1[1]);  // closing pipe1 write end
        close(pipefds2[0]);  // closing pipe2 read end

        /************************************
         * read from pipe1 in parent...     *
         * *********************************/

        if (read(pipefds1[0], readmessage, sizeof(readmessage)) != -1) {
            // Read failed if -1
            printf("In Child: Reading from pipe 1 – Message is %s\n", readmessage);
            printf("In Child: Writing to pipe 2 – Message is %s\n", pipe2writemessage);
            /************************************
             * Writing into pipe2 from parent   *
             * *********************************/
        }
        if (write(pipefds2[1], pipe2writemessage, sizeof(pipe2writemessage)) == -1) {
            perror("Error ");
        }
    }

    return EXIT_SUCCESS;
}