dlopen 加载so库

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

int main(int argc, char **argv) {
	void *handle;
	double (*cosine)(double);
	char *error;  

	handle = dlopen ("/tmp/libtest.so", RTLD_LAZY);
	if (!handle) {
		fprintf (stderr, "%s ", dlerror());
		exit(1);
	}  

	cosine = (double(*)(double))dlsym(handle, "cos");
	if ((error = dlerror()) != NULL)  {
		fprintf (stderr, "%s ", error);
		exit(1);
	}  

	printf ("%f ", (*cosine)(2.0));
	dlclose(handle);
	return 0;
}