Simple Utility to find the path to a dynamic library on your system (by name)

dlfind.c

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

#ifdef __APPLE__
#include <mach-o/dyld.h>
#else // Linux
#include <link.h>
#endif

// So much of this is borrowed from Julia, here:
// https://github.com/JuliaLang/julia/blob/0027ed143e90d0f965694de7ea8c692d75ffa1a5/src/sys.c#L565-L626


const char *dlpath(void *handle) {
    const char *path = NULL;
#ifdef __APPLE__
    for (int32_t i = _dyld_image_count(); i >= 0 ; i--) {

        bool found = FALSE;
        const char *probe_path = _dyld_get_image_name(i);
        void *probe_handle = dlopen(probe_path, RTLD_NOW | RTLD_LOCAL | RTLD_NOLOAD);

        if (handle == probe_handle) {
            found = TRUE;
            path = probe_path;
        }

        dlclose(probe_handle);

        if (found)
            break;
    }
#else // Linux
    struct link_map *map;
    dlinfo(handle, RTLD_DI_LINKMAP, &map);

    if (map)
        path = map->l_name;
#endif
    return path;
}

int main(int argc, const char ** argv)
{
    if (argc != 2 || argc != 3) {
        fprintf(stderr, "Usage: %s [ <libfirst.dylib> ] <libfind.dylib>\n", argv[0]);
        fprintf(stderr, "Prints filesystem path to libfind.dylib (maybe loading libfirst.dylib first)\n");
        return 1;
    }

    const char *load_name = argv[1];
    const char *find_name = argv[2] ? argv[2] : load_name;

    void *load_handle = dlopen(load_name, RTLD_NOW | RTLD_LOCAL);
    void *find_handle = dlopen(find_name, RTLD_NOW | RTLD_LOCAL | RTLD_NOLOAD);

    if (!find_handle) {
        fprintf(stderr, "Could Not Open find lirbary: %s\n", dlerror());
        dlclose(load_handle);
        return 1;
    }

    const char *find_path = dlpath(find_handle);

    if (find_path) {
        printf("%s: %s\n", find_name, find_path);
    } else {
        fprintf(stderr, "%s not found\n", find_name);
    }

    dlclose(find_handle);
    dlclose(load_handle);

    return !find_path;
}