What is Ld_preload?

Shared libraries (also called dynamic libraries) are linked into the program in two stages . First, during compile time, the linker verifies that all the symbols (again, functions, variables and the like) required by the program, are either linked into the program, or in one of its shared libraries.

In Unix and Unix-like operating systems, a soname is a field of data in a shared object file . The soname is a string, which is used as a “logical name” describing the functionality of the object. Typically, that name is equal to the filename of the library, or to a prefix thereof, e.g. libc. so.

A shared object is an indivisible unit that is generated from one or more relocatable objects . Shared objects can be bound with dynamic executables to form a runable process. As their name implies, shared objects can be shared by more than one application.

LD_PRELOAD is an optional environmental variable containing one or more paths to shared libraries, or shared objects, that the loader will load before any other shared library including the C runtime library (libc.so) This is called preloading a library.