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


int main(int argc, char **argv) 
{

  void *handle;
  char buf[512], *error;
  long int (*convert)(char *);
  
  /* check for argument */
  if (argc < 2) {
    fprintf(stderr, "usage: %s <integer>\n", argv[0]);
    exit(1);
  }


  /* load shared library function */

  if (!getcwd(buf, sizeof(buf) - 1)) {
    fprintf(stderr, "failed to obtain current directory");
    exit(1);
  }

  strncat(buf, "/libconvert.so", sizeof(buf) - (strlen(buf) + 1));

  fprintf(stdout, "using: %s\n", buf);

  handle = dlopen (buf, RTLD_NOW);
  if (!handle) {

    fprintf(stderr, "falling back to default lib ...\n");

    if (!(handle = dlopen("/usr/local/lib/libconvert.so", RTLD_NOW))) {
      fputs(dlerror(), stderr);
      exit(1);
    }
  }

  convert = dlsym(handle, "atoi");
  if ((error = dlerror()) != NULL) {
    fputs(error, stderr);
    exit(1);
  }

  
  /* convert first argument to integer and multiply by two */
  fprintf(stdout, "%ld\n", 2 * (*convert)(argv[1]));


  /* cleanup */
  dlclose(handle);
  exit(0);
}