logdlopen.c

#define _GNU_SOURCE  
#include <dlfcn.h>
#include <stdio.h>

typedef void* (*real_dlopen_t)(const char*, int);

void*
real_dlopen(const char *filename, int flags) {
  return ((real_dlopen_t)dlsym(RTLD_NEXT, "dlopen"))(filename, flags);
}

void*
dlopen(const char *filename, int flags) {
  printf("Loading library %s\n", filename);
  void *result = real_dlopen(filename, RTLD_NOW);
  char *error = dlerror();

  if (error != NULL) {
    printf(error);
  }

  return result;
}

compile with gcc -shared -fPIC -o logdlopen.so logdlopen.c and do LD_PRELOAD=./logdlopen.so my_command