cat.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>


int main(int argc, char *args[]){
    if(argc != 2){
      printf("syntaxe incorrecte");
      return EXIT_FAILURE;
    }
    int nb_read, t_write, size = 1024;
    int *buffer = malloc(sizeof(int)*size);
    int nb_write;
    int descriptor = open(args[1], O_RDONLY);
    if(descriptor < 0){
        printf("impossible lire le fichier");
        return EXIT_FAILURE;
    }
    do{
       nb_read = read(descriptor, buffer, size);
       t_write = 0;
       do{
          nb_write = write(STDOUT_FILENO, (const void *)buffer, nb_read);
          t_write += nb_write;
       }while(nb_write < nb_read);

    }while( nb_read > 0);
    close(descriptor);
    return EXIT_SUCCESS;
}

This is an implementation of the cat function on UNIX like systems