Why change in LD_LIBRARY_PATH at Runtime dosen't Reflect on the Executable once the Executable gets loaded

Question

I'm trying to change the LD_LIBRARY_PATH from my C++ program. I'm able to get its value using getenv("LD_LIBRARY_PATH") and set its value using setenv() (and I know that this is working, because when I call getenv("LD_LIBRARY_PATH") again, I get the updated value), but changing its value from inside the program isn't having any effect on it: I still get this error-message:

Failed to Load the shared library file

If I set the value before the executable gets loaded or the application is started, it works fine.

Sennight

I would simply code a shell wrapper which sets appropriately the LD_LIBRARY_PATH before exec-ing the binary ELF executable. This is common practice (most distributions are doing this for firefox) – Academician

hi Basile thanks for your response right. I'm trying to write a shell wrapper as you said , But the problem is i need to run the script as . filename.sh (in the terminal) then only the export path works. if I try to start my application at system start up ,I'm not able to achieve the same . – Sennight

No, just chmod a+x filename.sh, put filename.sh inside some directory in your PATH and you can run it simply as filename.sh – Academician

I'm starting my application at system start up with application.sh which executes the filename.sh(shell script to set path) but it dosen't work ,the path is not set – Sennight

Then use a full path like e.g. $HOME/bin/filename.sh or /usr/local/bin/filename.sh. Look inside firefox or mozilla ; it is generally a shell script.... – Academician

Answer 1

Unfortunately setting LD_LIBRARY_PATH from within a running program will have no effect on it. The reason for this is that LD_LIBRARY_PATH is processed by the dynamic link loader (ld.so), which is the program which starts your program. Your program itself doesn't process LD_LIBRARY_PATH so changing it will have no effect.

Hargis

Changing LD_LIBRARY_PATH has no effect, except if the program calls after dlopen to load a plugin. – Academician

Agreed. Any child processes (of the original process) would inherit a change in LD_LIBRARY_PATH made within that original process. So, setting LD_LIBRARY_PATH within your program, then forking and killing the parent should put you where (I presume) you want to be in terms of the load path. – Hargis