Cannot find lib in path

Question

I am trying to start a program that relies on some libraries that are in my path, however, the program says it cannot find the files:

11:45:27 ~ > echo $PATH
/usr/share/fsl/5.0/bin:/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/home/mri/Scripts:/home/mri/Scripts/MRI:/home/mri/Software/BRAINS3/bin:/home/mri/Software/BRAINS3/lib:/home/mri/Software/ITK_Build/bin:/home/mri/Software/ITK_Build/lib:/home/mri/Software/VTK_Build/bin:/home/mri/Software/VTK_Build/lib:/usr/lib/fsl/5.0

11:45:33 ~ > brains3
/home/mri/Software/BRAINS3/bin/brains3_real: error while loading shared libraries: libiplUtils.so: cannot open shared object file: No such file or directory

11:45:35 ~ > sudo find / -name libiplUtils.so
[sudo] password for mri: 
/home/mri/Software/BRAINS3/lib/libiplUtils.so

Does anybody have an idea how to fix this?

Answer 1

You can specify the library search path with the environment variable LD_LIBRARY_PATH.

$ export LD_LIBRARY_PATH=/home/mri/Software/BRAINS3/lib
$ brains3

You shouldn't set this variable for your whole system. If you can't/don't want to install the software system wide you could create a wrapper script.

Answer 2

The dynamic linker searches for libraries en LD_LIBRARY_PATH.

Answer 3

Unix systems tend to sort different types of files into different directories. There are separate directories for executables (e.g. /usr/bin), documentation (e.g. /usr/man, /usr/info, …), native libraries (e.g. /usr/lib), Perl libraries (e.g. /usr/lib/perl5), and so on. Correspondingly, there are different path variables, all with the same syntax (colon-separated list of directories): PATH for executables, MANPATH for man pages, LD_LIBRARY_PATH for native libraries¹, PERL5LIB for Perl libraries, and so on.

For native libraries, there are system default libraries that are in the search path whether mentioned in the LD_LIBRARY_PATH environment variable or not. On Linux, these directories are listed in /etc/ld.so.conf (also, /lib and /usr/lib are always in the search path).

You therefore have several possibilities:

• Add /home/mri/Software/BRAINS3/lib to /etc/ld.so.conf (Linux-specific, other unix variants may have a similar file). Run ldconfig to make the change take effect.
• Add export LD_LIBRARY_PATH=/home/mri/Software/BRAINS3/lib in /etc/profile (applies to all users) or in ~/.profile (applies only to you).

• Make a wrapper script:

  #!/bin/sh
  export LD_LIBRARY_PATH=/home/mri/Software/BRAINS3/lib
  exec /home/mri/Software/BRAINS3/bin/brains3 "$@"
  

• Create symbolic links to the libraries in /home/mri/Software/BRAINS3/lib in another directory on the search path:

  ln -s /home/mri/Software/BRAINS3/bin/brains3/lib*.so.* /usr/local/lib/
  

¹ _{LD_LIBRARY_PATH is the name on most unix variants, but Mac OS X uses DYLD_LIBRARY_PATH instead.}