Differences between LD_PRELOAD and LD_LIBRARY_PATH

LD_PRELOADis a list of specific libraries (files) to be loaded before any other libraries, whether the program wants it or not. LD_LIBRARY_PATH is a list of directories to search when loading libraries that would have been loaded anyway. On linux you can read man ld.so for more information about these and other environment variables that affect the dynamic linker.