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Shared libraries are compiled code which is intended to be shared among several different programs. They are distributed as . so files in /usr/lib/. A library exports symbols which are the compiled versions of functions, classes and variables.
By default, libraries are located in /usr/local/lib, /usr/local/lib64, /usr/lib and /usr/lib64; system startup libraries are in /lib and /lib64. Programmers can, however, install libraries in custom locations. The library path can be defined in /etc/ld.
Where do I add shared libraries in Linux?
Sometimes in Linux when you install a new software package the instructions tell you to add a directory of shared libraries to your $LD_LIBRARY_PATH environment variable in your .bashrc. You may have noticed that if you then create a shortcut icon on your desktop to this application it won’t start because it can’t find the libraries.
Dynamically loaded libraries – the program takes full control by calling functions with the library. Shared libraries are named in two ways: the library name (a.k.a soname) and a “filename” (absolute path to file which stores library code).
In addition, there’s the name that the compiler uses when requesting a library, (I’ll call it the “linker name”), which is simply the soname without any version number. The key to managing shared libraries is the separation of these names. Programs, when they internally list the shared libraries they need, should only list the soname they need.
Where are shared libraries placed in the filesystem?
Shared libraries must be placed somewhere in the filesystem. Most open source software tends to follow the GNU standards; for more information see the info file documentation at info:standards#Directory_Variables.