/*
** From: paulm@solbourne.com (Paul Maybee)
**
** Here is the code to interpose a user function before a library function.
** If you place this into your own shared library (compile -pic) then this
** should work for an existing program.
**
** NOTE :- you must include library libdl.a in complation (-ldl)
*/

#include <dlfcn.h>

void *
libopen(function)
char *function;
/* Open dynamic library and return a pointer to the function specified */
{
  static void *library = (void *)0;
  void *fptr;
  char *err;

  if( !library ) {
    library = dlopen("libc.so", RTLD_LAZY);  /* open library */
    if (!library) {
      err = dlerror();
      if (err) printf("DL_Open (dlopen): %s\n", err);
      abort();
    }
  }
  fptr = dlsym(library, function);          /* get the function */
  if (!fptr) {
    err = dlerror();
    if (err) printf("DL_Open (dlsym): %s\n", err);
    abort();
  }
  return(fptr);
}

#ifdef TEST
#include <sys/param.h>
char *getwd(name)
char *name;
{ char *(*fptr)() = (char *(*)())libopen("getwd");
  printf("Interposing my function\n");
  return (*fptr)(name);   /* call the real getwd */
}
main()
{ char path[MAXPATHLEN];
  (void)getwd(path);
  printf("path = %s\n", path);
  return(0);
}
#endif