runpath

Runpath is a term used in computing to describe the runtime library search path that a dynamic linker uses to locate shared libraries needed by an executable or shared object. In ELF binaries, the runpath information is stored in the dynamic section as the DT_RUNPATH tag (often referred to simply as RUNPATH). It is related to, but distinct from, the older RPATH mechanism.

The runpath specifies directories that the dynamic loader should search for dependencies at load time. Its purpose is to guide the linker in locating shared libraries without requiring hard-coded absolute paths. The exact order and interaction with environment variables can vary by platform and linker, but in general the search considers the runpath together with other sources such as environment variables (notably LD_LIBRARY_PATH) and default system library directories.

A related concept is RPATH, which historically served a similar role but had different precedence rules with respect to LD_LIBRARY_PATH. RUNPATH was introduced to allow runtime overrides by the environment while maintaining a stable, embedded path in the binary. This makes RUNPATH more flexible for packaging and distribution, especially in systems that rely on different library versions.

Practically, runpath can be inspected with tools such as readelf or objdump, and its contents can be influenced at build time with linker options that embed a runtime search path (for example, certain -rpath-related options). Understanding runpath is important for software packaging, deployment, and environments where multiple library versions coexist, such as containers or cross-compiled systems.