freepascal.compiler/docs/progex/ctest2.c

#include <dlfcn.h>
#include <string.h>

int main()
{
    void *lib;
    char *s;
    int FromPos, ToPos;
    char* (*SubStr)(const char*, int, int);

    lib = dlopen("./libsubs.so", RTLD_LAZY);
    SubStr = dlsym(lib, "SUBSTR");

    s = strdup("Test");
    FromPos = 2;
    ToPos = 3;
    printf("Result from SubStr: '%s'\n", (*SubStr)(s, FromPos, ToPos));
    dlclose(lib);
    return 0;
}