Online note taking app - Notes.ionotes

Fast | Easy | Short

Online Note Services - notes.io

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

// some macros to make the code more understandable
// regarding which pipe to use to a read/write operation
//
// Parent: reads from P1_READ, writes on P1_WRITE
// Child: reads from P2_READ, writes on P2_WRITE
#define P1_READ 0
#define P2_WRITE 1
#define P2_READ 2
#define P1_WRITE 3

// the total number of pipe *pairs* we need
#define NUM_PIPES 2

int main(int argc, char *argv[])
{
int fd[2*NUM_PIPES];
int val = 0, len, i;
pid_t pid;

// create all the descriptor pairs we need
for (i=0; i<NUM_PIPES; ++i)
{
if (pipe(fd+(i*2)) < 0)
{
perror("Failed to allocate pipes");
exit(EXIT_FAILURE);
}
}

// fork() returns 0 for child process, child-pid for parent process.
if ((pid = fork()) < 0)
{
perror("Failed to fork process");
return EXIT_FAILURE;
}

// if the pid is zero, this is the child process
if (pid == 0)
{
// Child. Start by closing descriptors we
// don't need in this process
close(fd[P1_READ]);
close(fd[P1_WRITE]);

// used for output
pid = getpid();

// wait for parent to send us a value
len = read(fd[P2_READ], &val, sizeof(val));
if (len < 0)
{
perror("Child: Failed to read data from pipe");
exit(EXIT_FAILURE);
}
else if (len == 0)
{
// not an error, but certainly unexpected
fprintf(stderr, "Child: Read EOF from pipe");
}
else
{
// report what we received
printf("Child(%d): Received %dn", pid, val);

// now double it and send it back
val *= 2;

printf("Child(%d): Sending %d backn", pid, val);
if (write(fd[P2_WRITE], &val, sizeof(val)) < 0)
{
perror("Child: Failed to write response value");
exit(EXIT_FAILURE);
}
}

// finished. close remaining descriptors.
close(fd[P2_READ]);
close(fd[P2_WRITE]);

return EXIT_SUCCESS;
}

// Parent. close unneeded descriptors
close(fd[P2_READ]);
close(fd[P2_WRITE]);

// used for output
pid = getpid();

// send a value to the child
val = 42;
printf("Parent(%d): Sending %d to childn", pid, val);
if (write(fd[P1_WRITE], &val, sizeof(val)) != sizeof(val))
{
perror("Parent: Failed to send value to child ");
exit(EXIT_FAILURE);
}

// now wait for a response
len = read(fd[P1_READ], &val, sizeof(val));
if (len < 0)
{
perror("Parent: failed to read value from pipe");
exit(EXIT_FAILURE);
}
else if (len == 0)
{
// not an error, but certainly unexpected
fprintf(stderr, "Parent(%d): Read EOF from pipe", pid);
}
else
{
// report what we received
printf("Parent(%d): Received %dn", pid, val);
}

// close down remaining descriptors
close(fd[P1_READ]);
close(fd[P1_WRITE]);

// wait for child termination
wait(NULL);

return EXIT_SUCCESS;
}
     
 
what is notes.io
 

Notes.io is a web-based application for taking notes. You can take your notes and share with others people. If you like taking long notes, notes.io is designed for you. To date, over 8,000,000,000 notes created and continuing...

With notes.io;

  • * You can take a note from anywhere and any device with internet connection.
  • * You can share the notes in social platforms (YouTube, Facebook, Twitter, instagram etc.).
  • * You can quickly share your contents without website, blog and e-mail.
  • * You don't need to create any Account to share a note. As you wish you can use quick, easy and best shortened notes with sms, websites, e-mail, or messaging services (WhatsApp, iMessage, Telegram, Signal).
  • * Notes.io has fabulous infrastructure design for a short link and allows you to share the note as an easy and understandable link.

Fast: Notes.io is built for speed and performance. You can take a notes quickly and browse your archive.

Easy: Notes.io doesn’t require installation. Just write and share note!

Short: Notes.io’s url just 8 character. You’ll get shorten link of your note when you want to share. (Ex: notes.io/q )

Free: Notes.io works for 12 years and has been free since the day it was started.


You immediately create your first note and start sharing with the ones you wish. If you want to contact us, you can use the following communication channels;


Email: [email protected]

Twitter: http://twitter.com/notesio

Instagram: http://instagram.com/notes.io

Facebook: http://facebook.com/notesio



Regards;
Notes.io Team

     
 
Shortened Note Link
 
 
Looding Image
 
     
 
Long File
 
 

For written notes was greater than 18KB Unable to shorten.

To be smaller than 18KB, please organize your notes, or sign in.