Question

Write a C program that uses two FIFOs to enable bidirectional communication between a parent and child process. The parent process should loop reading a block of text from standard input and use one of the pipes to send the text to the child, which converts it to uppercase and sends it back to the parent via the other pipe. The parent reads the data coming back from the child and echoes it on standard output before continuing around the loop once more.

Answer 1

#include<stdio.h>

#include<stdlib.h>

#include<unistd.h>

#include<sys/types.h>
#include <ctype.h>

#include<string.h>

#include<sys/wait.h>
int main()

{

// We will use two pipes

// First pipe to send the text from parent to the child

// Second pipe to send the converted string from child

int pipe_1[2]; // Used to store two ends of first pipe

int pipe_2[2]; // Used to store two ends of second pipe
char input_str[100];
pid_t p;
if (pipe(pipe_1)==-1)
{
fprintf(stderr, "Pipe Failed" );
return 1;
}
if (pipe(pipe_2)==-1)
{
fprintf(stderr, "Pipe Failed" );
return 1;
}
scanf("%s", input_str);
p = fork();
if (p < 0)
{
fprintf(stderr, "fork Failed" );
return 1;
}// Parent process
else if (p > 0)
{char uppercase_str[100];
close(pipe_1[0]); // Close reading end of first pipe
// Write input string and close writing end of first pipe.
write(pipe_1[1], input_str, strlen(input_str)+1);
close(pipe_1[1]);
// Wait for child to send a string
wait(NULL);
close(pipe_2[1]); // Close writing end of second pipe
// Read string from child, print it and close
// reading end.
read(pipe_2[0], uppercase_str, 100);
printf("Your string in uppercase %s\n", uppercase_str);
close(pipe_2[0]);
}
// child process
else
{close(pipe_1[1]); // Close writing end of first pipe
// Read a string using first pipe
char uppercase_str[100];
int length=read(pipe_1[0], uppercase_str, 100);
int k = strlen(uppercase_str);
int i;
for (int i = 0; i < k ; i++) {
uppercase_str[i] = toupper(uppercase_str[i]);
}
// Close both reading ends

close(pipe_1[0]);
close(pipe_2[0]);
// Write uppercase string and close writing end
write(pipe_2[1], uppercase_str, strlen(uppercase_str)+1);
close(pipe_2[1]);
exit(0);
}
}