Can I write this code without using file stream - c

Question

#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
/* Read characters from the pipe and echo them to stdout. */
void read_from_pipe (int file)
{
FILE *stream;
int c;
stream = fdopen (file, "r");
while ((c = fgetc (stream)) != EOF)
putchar (c);
fclose (stream);
}
/* Write some random text to the pipe. */
void write_to_pipe (int file)
{
FILE *stream;
stream = fdopen (file, "w");
fprintf (stream, "Hello from Parent!\n");
fclose (stream);
}
int main (void)
{
int pid;
int mypipe[2];
/* Create the pipe. */
if (pipe (mypipe))
{
printf("Pipe failed.\n");
return EXIT_FAILURE;
}
/* Create the child process. */
pid = fork ();
if (pid == 0)
{
/* This is the child process.
Close other end first. */
close (mypipe[1]);
read_from_pipe (mypipe[0]);
return EXIT_SUCCESS;
}
else if (pid < 0)
{
/* The fork failed. */
printf ("Fork failed.\n");
return EXIT_FAILURE;
}
else
{
/* This is the parent process.
Close other end first. */
close (mypipe[0]);
write_to_pipe (mypipe[1]);
return EXIT_SUCCESS;
}
}
I want to write simple program to do this task:
Parent process creates a pipe using the pipe() system call.
Parent process creates a child process.
Parent process sends a message "Hello from Parent" to the child.
Child process prints the message to the screen.
This code creates File stream. I can't understand why. Without file stream can I do this thing..?

Answer 1

This answer may be helpful for a future Googler.
I guess this is what you are looking for.
Here is what I wrote:
#include <stdio.h>
#include <unistd.h>
int main(){
int p, f;
int rw_setup[2];
char message[20];
p = pipe(rw_setup);
if(p < 0){
printf("An error occured. Could not create the pipe.");
_exit(1);
}
f = fork();
if(f > 0){
write(rw_setup[1], "Hello from Parent", 18);
}
else if(f == 0){
read(rw_setup[0],message,18);
printf("%s %d\n", message, r_return);
}
else{
printf("Could not create the child process");
}
return 0;
}
To create child process we use fork(). fork() returns :
<0 fail to create child (new) process
=0 for child process
>0 i.e process ID of the child process to the parent process. When >0 parent process will execute.
pipe() is used for passing information from one process to another. pipe() is unidirectional therefore, for two-way communication between processes, two pipes can be set up, one for each direction.
You can read more details here.

Answer 2

You can also use File descriptors.
Basically, when you call pipe(), the operating system prepares two file descriptors and writes their "names" to the argument (mypipe in this case).
You can use these file descriptors without opening any file streams by using the standard operating system calls: write(), read(), close(), etc.