How to check what shared libraries are loaded at run time for a given process?

Actually, you can do this in your code in the following way:

#include <link.h>

using UnknownStruct = struct unknown_struct {
   void*  pointers[3];
   struct unknown_struct* ptr;
};
using LinkMap = struct link_map;

auto* handle = dlopen(NULL, RTLD_NOW);
auto* p = reinterpret_cast<UnknownStruct*>(handle)->ptr;
auto* map = reinterpret_cast<LinkMap*>(p->ptr);

while (map) {
  std::cout << map->l_name << std::endl;
  // do something with |map| like with handle, returned by |dlopen()|.
  map = map->l_next;
}

The link_map structure contains at least the base address and the absolute file name. It's the structure that is actually returned by dlopen() with non-NULL first argument. For more details see here.

Other people are on the right track. Here are a couple ways.

cat /proc/NNNN/maps | awk '{print $6}' | grep '\.so' | sort | uniq

Or, with strace:

strace CMD.... 2>&1 | grep -E '^open(at)?\(.*\.so'

Both of these assume that shared libraries have ".so" somewhere in their paths, but you can modify that. The first one gives fairly pretty output as just a list of libraries, one per line. The second one will keep on listing libraries as they are opened, so that's nice.

And of course lsof...

lsof -p NNNN | awk '{print $9}' | grep '\.so'

May be lsof - the swiss army knife of linux will help?

edit: to run, lsof -p <pid>, lists all sorts of useful information, for example, if the process is java, lists all the open jars - very cool...