LD_LIBRARY_PATH failing while trying to run Qt app

I want to run a Qt 5 based application usind dynamic libraries on Linux. In summary, a script will copy the executable and other relevant files, including all required .so inside a lib folder, to the desired destination and a script calling gksudo will work as caller to the app.

Till now everything works fine till I call the executable script: the app doesn’t run. When I ask to run with sudo, it tells me that a library (Qt5SerialPort…) is missing. Running ldd over the actual executable I discover that the app is getting the required libs not from within the lib folder, but some apparent hard-coded paths.

I tried to solve this by using qt.conf but got no success. As note here, it would seem qt.conf isn’t actually supposed to work this way. Consulting the Qt documentation, I decided to use LD_LIBRARY_PATH to tell the linker where to find the libs since I was already using a script to run the app anyway. So the final, summarized script code is

#!/bin/sh
LD_LIBRARY_PATH=lib/
export LD_LIBRARY_PATH
sudo ldconfig #sometimes  sudo /sbin/ldconfig -v
gksudo "$INSPATH/myApp" #or sudo instead

Problem is that it is still not working. When I call echo $LD_LIBRARY_PATH, I can see the variable was properly edited, but when I call the run line (with sudo), it keeps telling me that lib wasn’t found.

What am I missing?

Answer

sudo doesn’t pass LD_LIBRARY_PATH:

$ LD_LIBRARY_PATH=lib/
$ export LD_LIBRARY_PATH
$ env | grep LD_LIBRARY_PATH
LD_LIBRARY_PATH=lib/
$ sudo env | grep LD_LIBRARY_PATH

You can set it for the command run as root:

$ sudo env LD_LIBRARY_PATH=/lib env | grep LD_LIBRARY_PATH
SUDO_COMMAND=/usr/bin/env LD_LIBRARY_PATH=/lib env
LD_LIBRARY_PATH=/lib

You’ll want something like

sudo env LD_LIBRARY_PATH=/lib "$INSPATH/myApp"

As always, be careful with sudo!