Read the dlopen(3) man page (e.g. by typing man dlopen
in a terminal on your machine):
If filename contains a slash ("/"), then it is interpreted as a (relative or absolute) pathname. Otherwise, the dynamic linker searches for the library as follows (see ld.so(8) for further details):
o (ELF only) If the executable file for the calling program
contains a DT_RPATH tag, and does not contain a DT_RUNPATH tag,
then the directories listed in the DT_RPATH tag are searched.
o If, at the time that the program was started, the environment
variable LD_LIBRARY_PATH was defined to contain a colon-separated
list of directories, then these are searched. (As a security
measure this variable is ignored for set-user-ID and set-group-ID
programs.)
o (ELF only) If the executable file for the calling program
contains a DT_RUNPATH tag, then the directories listed in that
tag are searched.
o The cache file /etc/ld.so.cache (maintained by ldconfig(8)) is
checked to see whether it contains an entry for filename.
o The directories /lib and /usr/lib are searched (in that order).
So you need to call dlopen("./libLibraryName.so", RTLD_NOW)
-not just dlopen("libLibraryName.so", RTLD_NOW)
which wants your plugin to be in your $LD_LIBRARY_PATH
on in /usr/lib/
etc .... - or add .
to your LD_LIBRARY_PATH
(which I don't recommend for security reasons).
As Jhonnash answered you should use and display the result of dlerror
when dlopen
(or dlsym
) fails:
void* dlh = dlopen("./libLibraryName.so", RTLD_NOW);
if (!dlh)
{ fprintf(stderr, "dlopen failed: %s\n", dlerror());
exit(EXIT_FAILURE); };
You might want to read some books like Advanced Linux Programming to get some knowledge about Linux system programming in general.