inter-process communication with data sending in c

Question

I am in a scenario where I have to write a program that creates two processes. The father process opens a text file for reading. It is assumed that the file is composed of words formed of alphabetic characters separated by spaces. The child process enters a word on the keyboard. The father process looks for the word in the file, and passes to the child the value 1 if the word is in the file, and 0 otherwise. The son displays the result.

Here I think used the tubes for communication between these processes. However, this communication seems to me difficult. Does this ordering: process father-process son-process father-process son is possible?

Answer 1

Attaching a simple pipe program for basic understanding. One can modify according to her needs.

/* simple_pipe.c

   Simple demonstration of the use of a pipe to communicate
   between a parent and a child process.

   Usage: simple_pipe "string"

   The program creates a pipe, and then calls fork() to create a child process.
   After the fork(), the parent writes the string given on the command line
   to the pipe, and the child uses a loop to read data from the pipe and
   print it on standard output.
*/

#include <sys/wait.h>
#include "tlpi_hdr.h"

#define BUF_SIZE 10

int
main(int argc, char *argv[])
{
    int pfd[2];                             /* Pipe file descriptors */
    char buf[BUF_SIZE];
    ssize_t numRead;

    if (argc != 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s string\n", argv[0]);

    if (pipe(pfd) == -1)                    /* Create the pipe */
        errExit("pipe");

    switch (fork()) {
    case -1:
        errExit("fork");

    case 0:             /* Child  - reads from pipe */
        if (close(pfd[1]) == -1)            /* Write end is unused */
            errExit("close - child");

        for (;;) {              /* Read data from pipe, echo on stdout */
            numRead = read(pfd[0], buf, BUF_SIZE);
            if (numRead == -1)
                errExit("read");
            if (numRead == 0)
                break;                      /* End-of-file */
            if (write(STDOUT_FILENO, buf, numRead) != numRead)
                fatal("child - partial/failed write");
        }

        write(STDOUT_FILENO, "\n", 1);
        if (close(pfd[0]) == -1)
            errExit("close");
        _exit(EXIT_SUCCESS);

    default:            /* Parent - writes to pipe */
        if (close(pfd[0]) == -1)            /* Read end is unused */
            errExit("close - parent");

        if (write(pfd[1], argv[1], strlen(argv[1])) != strlen(argv[1]))
            fatal("parent - partial/failed write");

        if (close(pfd[1]) == -1)            /* Child will see EOF */
            errExit("close");
        wait(NULL);                         /* Wait for child to finish */
        exit(EXIT_SUCCESS);
    }
}

Have a look on more examples here on Chapter-44 The Linux Programming Interface. Keep this book on your table or e-book on you computer, it's a bible for Linux programming.