dlsym()

NAME

dlsym() - get the address of a symbol from a dynamically-linked object

SYNOPSIS

#include <dlfcn.h>


void *dlsym(void *handle, const char *name)

The dlsym(3) call retrieves the address of a symbol defined in the object referenced by handle. The object must have already been opened by a call to dlopen(3). The symbol is stored in name as a character string.

If loading the object referenced by handle caused other objects to be automatically loaded, all of those objects are searched by the dlsym(3) call. Dlsym(3) operations on the global symbol object use load ordering. However, the symbols are resolved in dependency order (see the dlopen(3) reference page).

RETURN VALUES

The dlsym(3) call returns NULL if the handle doesn't refer to a valid object, or if the symbol can't be found in any of the objects associated with handle. For more detailed information, use dlerror(3).

EXAMPLE

Here's a brief example of using dlopen(3) and dlsym(3):

void *handle;
int  *iptr, (*fptr)(int);
/* open the object */
handle = dlopen("/usr/lib/libc.so", RTLD_LAZY);
/* find the address of a data object */
iptr = (int *)dlsym(handle, "an_object");
/* find the address of a function */
fptr = (int (*)(int))dlsym(handle, "a_function");

NOTES

There is a special purpose value for handle, RTLD_NEXT, that is reserved for future use.