The dlsym() function allows a process to obtain the address of a symbol defined within a shared object or executable. The handle argument is either the value returned from a call to dlopen() or one of the special handles RTLD_DEFAULT, RTLD_NEXT, or RTLD_SELF. The name argument is the symbol's name as a character string.
In the case of a handle returned from dlopen(), the corresponding shared object must not have been closed using dlclose(). The dlsym() function searches for the named symbol in all shared objects loaded automatically as a result of loading
the object referenced by handle. See dlopen(3DL).
In the case of the special handle RTLD_DEFAULT, dlsym() searches for the named symbol starting with the first object loaded and proceeding through the list of initial loaded objects, and any global objects obtained with dlopen(3DL), until a match is found. This search follows the default model employed to relocate all objects within the process.
In the case of the special handle RTLD_NEXT, dlsym() searches for the named symbol in the objects that were loaded following the object from which the dlsym() call is being made.
In the case of the special handle RTLD_SELF, dlsym() searches for the named symbol in the objects that were loaded starting with the object from which the dlsym() call is being made.
In the case of RTLD_DEFAULT, RTLD_NEXT, and RTLD_SELF, if the objects being searched have been loaded from dlopen() calls, dlsym() searches
the object only if the caller is part of the same dlopen() dependency hierarchy, or if the object was given global search access. See dlopen(3DL) for a discussion of the RTLD_GLOBAL mode.
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