How to correctly add variable to environment or session

Question

I work with a opensource software that I have built locally. After build the manual says to run it like this while inside the build directory

$ LD_LIBRARY_PATH=../applicationExeFile

Then the application runs fine.

Now I tried to make a simple shell to call quickly without typing much (run.sh) with the following content:

#!/bin/bash

export -n LD_LIBRARY_PATH=.
./applicationExeFile

But it seems that LD_LIBRARY_PATH does not get registered in shell as I get error regarding the application executable can not find a library that is in the same folder

./applicationExeFile: error while loading shared libraries: libchart.so: cannot open shared object file: No such file or directory

What am I doing wrong and how to achieve this?

Answer 1

The first issue is that -n actually unexports a variable, it doesn't export it. See help export:

export: export [-fn] [name[=value] ...] or export -p
    Set export attribute for shell variables.
    
    Marks each NAME for automatic export to the environment of subsequently
    executed commands.  If VALUE is supplied, assign VALUE before exporting.
    
    Options:
      -f    refer to shell functions
      -n    remove the export property from each NAME
      -p    display a list of all exported variables and functions
    
    An argument of `--' disables further option processing.
    
    Exit Status:
    Returns success unless an invalid option is given or NAME is invalid.

Next, . refers to the current working directory of the process. This means that your script still needs to be run from the specific directory where your program is installed which seems a bit pointless. Just use a full path instead. If your program is at /home/dekker/myprogram, make your script like this:

#!/bin/bash
export LD_LIBRARY_PATH=/home/dekker/myprogram
/home/dekker/myprogram/applicationExeFile

Or just:

#! /bin/sh -
LD_LIBRARY_PATH=/home/dekker/myprogram exec /home/dekker/myprogram/applicationExeFile

as there's nothing bash-specific, and you don't need the separate export statement. Using exec also saves a process and makes signal handling and the reporting of the exit status more reliable.