copy file content using posix in C.

copy_file_content.c

#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#define NMAX 100

int main(int argc, char **argv) {
    int src, dist, nb;
    char buffer[NMAX];
    /*** testing arguments ***/
    if (argc <3) {
        fprintf(stderr, "usage %s source destination \n", argv[0]);
        exit(EXIT_FAILURE);
    }
    /*** opening source file on read mode ***/
    src = open(argv[1], O_RDONLY);
    if (src == -1) {
        perror("error while opening source file");
        exit(EXIT_FAILURE);
    }
    /*** opening distination file on writing mode ***/
    /*** O_WRONLY, creates a file if doesn't exist and open it on writing mode ***/
    /*** O_CREAT, if the file exist delete everything in it using O_TRUNC ***/
    dist = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (dist == -1) {
        perror("error while opening destination file");
        exit(EXIT_FAILURE);
    }
    while (nb = read(src, buffer, NMAX) > 0) {
      if (write(dist, buffer, NMAX) > -1) {
        return -1;
      }
    }
    return 0;
}