Setting LD_LIBRARY_PATH environment variable for loading a shared library at runtime (g++)

Question

I'm having two problems related to the same issue:

1. I have a shared object saved in `pwd`/lib and while the executable that uses it compiles successfully (by using -l and -L switches), at runtime, it's giving me grief. If I try to run LD_LIBRARY_PATH=/my/absolute/path/to/library/directory ./test it works fine. But if I export LD_LIBRARY_PATH=/my/absolute/path/to/library/directory and do ./test it says that it can't find the shared library. However, if I do LD_LIBRARY_PATH=$LD_LIBRARY_PATH ./test again it works fine!! Any ideas on what I'm doing wrong?

2. Second issue is related to the exporting of the LD_LIBRARY_PATH env variable. If I open a terminal and type export LD_LIBRARY_PATH=/path/to/stuff and then type echo $LD_LIBRARY_PATH, the variable is correct. However if I write a script containing the export command, simply running it doesn't update the variable, instead I need to run source install.sh in order to actually persist the variable. What's the best solution for this?

Thank you for your time!

Answer 1

To answer the second question first:

source executes the script inside the current shell, ./install.sh opens and executes it in a different shell. http://www.unix.com/unix-dummies-questions-answers/537-difference-between-source-exec-script.html

Now for your first question:

LD_LIBRARY_PATH=$LD_LIBRARY_PATH ./test sets the LD_LIBRARY_PATH variable before just one command (the ./test command). For the same reason above, I believe this isn't getting transferred to whatever shell ./test creates. To make it persist, you may need to put the export LD_LIBRARY_PATH=... in your ~/.bashrc

Answer 2

I have found sometimes adding -L explicitly via the CFLAGS environment variable is successful when LD_RUN_PATH was not. As in: export CFLAGS=-L/opt/tool/lib