Inter-Process Communication in C

Description

This project contains a series of C programs that demonstrate various methods of inter-process communication (IPC) in Unix-like operating systems. These programs illustrate the use of pipes and named pipes (FIFOs) to facilitate communication between processes. Each file showcases different aspects of IPC, providing a comprehensive overview of how to implement these mechanisms in C.

Key Features

• Anonymous Pipes: Examples of using pipes for communication between a parent and child process.
• Named Pipes (FIFOs): Demonstrations of using named pipes to communicate between unrelated processes.
• Process Synchronization: Basic examples of synchronizing processes using IPC mechanisms.

Files

1. A1P7.c

   • Demonstrates the use of anonymous pipes for communication between a parent process and a child process.
   • Key Code Snippet:

     #include <stdio.h>
     #include <stdlib.h>
     #include <string.h>
     
     #define MAX 256
     
     int main() {
         int tuberia[2];
         int pid;
         char mensaje[MAX];
     
         if (pipe(tuberia) == -1) {
             perror("pipe");
             exit(-1);
         }
         if ((pid = fork()) == -1) {
             perror("fork");
             exit(-1);
         } else if (pid == 0) {
             while (read(tuberia[0], mensaje, MAX) > 0 && strcmp(mensaje, "FIN") != 0) {
                 printf("PROCESO RECEPTOR. MENSAJE: %s\n", mensaje);
             }
             close(tuberia[0]);
             close(tuberia[1]);
             exit(0);
         } else {
             while (printf("PROCESO EMISOR. MENSAJE:") != 0 && gets(mensaje) != NULL && write(tuberia[1], mensaje, strlen(mensaje) + 1) > 0 && strcmp(mensaje, "FIN") != 0);
             close(tuberia[0]);
             close(tuberia[1]);
             exit(0);
         }
     }

     This code creates a pipe and uses it to send messages from the parent process to the child process.

2. A2P7.c

   • Illustrates the use of two pipes for bidirectional communication between a parent process and a child process.
   • Key Code Snippet:

     #include <sys/types.h>
     #include <fcntl.h>
     #include <unistd.h>
     #include <stdio.h>
     #include <string.h>
     #include <stdlib.h>
     #include <wait.h>
     
     #define SIZE 512
     
     int main(int argc, char **argv) {
         pid_t pid;
         int a[2], b[2], readbytes;
         char buffer[SIZE];
     
         pipe(a);
         pipe(b);
     
         if ((pid = fork()) == 0) {
             close(a[1]);
             close(b[0]);
             while ((readbytes = read(a[0], buffer, SIZE)) > 0)
                 write(1, buffer, readbytes);
             close(a[0]);
             strcpy(buffer, "Soy tu hijo hablandote por la otra tuberia\n");
             write(b[1], buffer, strlen(buffer));
             close(b[1]);
         } else {
             close(a[0]);
             close(b[1]);
             strcpy(buffer, "Soy tu padre hablandote por una tuberia\n");
             write(a[1], buffer, strlen(buffer));
             close(a[1]);
             while ((readbytes = read(b[0], buffer, SIZE)) > 0)
                 write(1, buffer, readbytes);
             close(b[0]);
         }
         waitpid(pid, NULL, 0);
         exit(0);
     }

     This code sets up two pipes for bidirectional communication between the parent and child processes.

3. A3P7.c

   • Demonstrates the use of a named pipe (FIFO) to send a message from one process to another.
   • Key Code Snippet:

     #include <sys/stat.h>
     #include <unistd.h>
     #include <fcntl.h>
     #include <stdio.h>
     
     int main(void) {
         int fd;
         char buf[] = "Hola, pase por la tuberia";
         mkfifo("fifo2", 0666);
         fd = open("fifo2", O_WRONLY);
         write(fd, buf, sizeof(buf));
         close(fd);
         return 0;
     }

     This code creates a named pipe and writes a message to it.

4. receptor.c

   • Demonstrates reading a message from a named pipe (FIFO).
   • Key Code Snippet:

     #include <sys/stat.h>
     #include <unistd.h>
     #include <fcntl.h>
     #include <stdio.h>
     
     int main(void) {
         int fd, n;
         char buf[1024];
     
         fd = open("fifo2", O_RDONLY);
         n = read(fd, buf, sizeof(buf));
         printf("Numero de bytes rx: %d\n", n);
         printf("RX Mensaje: %s\n", buf);
         close(fd);
         return 0;
     }

     This code opens a named pipe and reads a message from it.

How to Use

1. Compilation: Each C file can be compiled using a C compiler such as gcc.

   gcc A1P7.c -o A1P7
   gcc A2P7.c -o A2P7
   gcc A3P7.c -o A3P7
   gcc receptor.c -o receptor

2. Execution:

   • Run the anonymous pipe example:

     ./A1P7

   • Run the bidirectional pipe example:

     ./A2P7

   • Run the named pipe examples:
     • First, run the receptor in one terminal:

       ./receptor

     • Then, run the sender in another terminal:

       ./A3P7