title: fopen() return NULL and errno is 0
body: <p>I tried to create a file (src), read read characters from it and copy them to another file (dst), when the name of the files I'm getting from the command line arguments but the fopen() function return NULL.
  I read here that i should use errno.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;errno.h&gt;
  void copyFile(char *src, char *dst);
  
  int main(int args, char **argv) {
      int option = args;
  
      if(option == 3){
         copyFile(argv[1], argv[2]);
      }
  
      return 0;
  }
  
  void copyFile(char *src, char *dst) {
      FILE *srcFile = fopen(src, "rb");
      FILE *dstFile = fopen(dst, "wb");
  
      if (srcFile || dstFile) {
          printf("Error %d \n", errno);
          return;
      } else {
          char buff[2];
          while (fread(buff, 2, 1, srcFile) != 0) {
              fwrite(buff, 2, 1, dstFile);
          }
          fclose(srcFile);
          fclose(dstFile);
      }
  }
  </code></pre>