LDLIBRARYPATH

LDLIBRARYPATH is not a standard, widely recognized environment variable in Unix-like systems. The correct and commonly used variable for controlling runtime shared library search paths is LD_LIBRARY_PATH. LDLIBRARYPATH may appear as a typo or as a user-defined alias in some scripts, but it is not interpreted by the dynamic linker in any standard way unless explicitly implemented in a shell or program.

LD_LIBRARY_PATH specifies a colon-separated list of directories that the dynamic linker should search for shared libraries at program startup and for dynamically loaded libraries (via dlopen). Directories listed there are consulted before the system’s default locations, such as /lib and /usr/lib, allowing users to override or test libraries in nonstandard locations. For example, export LD_LIBRARY_PATH=/custom/lib:/opt/mylibs would cause the linker to look in those directories first.

In practice, setting this variable affects how executables locate their dependencies and can influence which library versions are loaded. The exact search order and interaction with embedded runpath or rpath values in binaries depend on the linker and the operating system. While LD_LIBRARY_PATH can be useful for testing or development, it can introduce portability and security risks, and it may bypass system-wide library management provided by tools like ldconfig.

Best practices encourage installing libraries in standard locations or using binary-specific rpath/runpath settings, or configuring the system’s dynamic linker configuration, rather than relying on LD_LIBRARY_PATH. If LDLIBRARYPATH appears in scripts, treat it as likely a typo or a nonstandard alias for LD_LIBRARY_PATH. On other systems, such as macOS, analogous variables include DYLD_LIBRARY_PATH, which follows different rules.