Question

give code to set up a pipe or a FIFO for a parent process and it child process. have the child process send a message("i'm ok") to the parent process. the parent process should read the message into a buffer.

Answer 1

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<string.h>
#include<sys/wait.h>
  
int main()
{
// pipe() is used to transfer information from one process to another in unidirectional way
  
int fd[2]; // Used to store reading and writing ends of pipe

  
char fixed_str[] = "i'm ok";
pid_t p;
  
if (pipe(fd)==-1)
{
fprintf(stderr, "Pipe Failed" );
return 1;
}

p = fork();
  
if (p < 0)
{
fprintf(stderr, "fork Failed" );
return 1;
}
  
// Parent process
else if (p > 0)
{
// Read string into buffer from child and print the message.
char result_str[100];
  
//Wait for child to send message
wait(NULL);
  
//Read message from child and print the message
read(fd[0], result_str, 100);
printf("Message from child : %s\n", result_str);
close(fd[0]); //Close reading end
}
  
// child process
else
{
// Write message to be sent to parent
write(fd[1], fixed_str, strlen(fixed_str)+1);
close(fd[1]); //close writing end
  
exit(0);
}
}