rpath is an option used with the runtime linker (ld.so) to insert an RPATH header in either binaries or shared libraries. This header specifies the path search order for locating libraries.
rpath is an option used with the runtime linker on Unix and Linux (ld.so) to insert an RPATH header in either binaries or shared libraries. This header specifies the path search order for locating libraries.
The RPATH header is in the same format as the shell PATH variable, a list of directories separated by colons. There are some special tags that can be used which look like shell variables but which are really special commands to the shared library loader.
The most commonly used one is $ORIGIN which equals the current directory where the binary or shared library is located.
For instance, if I have ./x/bin/myprog and ./x/lib/libstuff.so.0 then I can make sure that myprog finds libstuff by setting its RPATH header to $ORIGIN/../lib. But if libstuff depends on libz then it will find that in /lib or /usr/lib. However, if I also set an RPATH header in libstuff.so.0 of $ORIGIN then it will first search ./x/lib for libz. Therefore I can copy libz to ./x/lib and also copy libstuff.so.0 to the same place and modify its RPATH.
If you are building and linking the software then you can control the RPATH header with the -rpath option. On linux you can also use a program named patchelf to fix it after the fact. The Solaris equivalent is elfedit.
To check out current RPATH header, run readelf -d libtest.so on Linux or elfdump -d libtest.so
Setting RPATH is a polite thing to do for a self-contained app that you need to distribute to users since it helps to remove opportunities for finding incorrect versions of libraries.
