Linux - Library Path (LD_LIBRARY_PATH, LIBPATH, SHLIB_PATH)

About

LD_LIBRARY_PATH is a environment variable that lists directory where executable can search for linux shared library. It's also called the shared library search path.

The value of the environment variable LD_LIBRARY_PATH is a colon-separated (:) set of directories where libraries are searched for first before the standard set of directories.

If you are running on a Solaris system, the LD_LIBRARY_PATH environment variable is used to define the native library path.

Articles Related

Why was it invented?

There were a couple good reasons why it was invented:

• This is useful when debugging a new library or using a non-standard library for special purposes, but be sure you trust those who can control those directories.
• To test out new library routines against an already compiled binary (for either backward compatibility or for new feature testing).
• To have a short term way out in case you wanted to move a set of shared libraries to another location.

Environment Variable

Search in it

Script search_library.sh where the first parameter is the library searched.

#!/bin/bash
IFS=:

for p in ${LD_LIBRARY_PATH}; do
    if [ -e ${p}/${1} ]; then
        echo ${p}
    fi
done

Example:

search_library.sh libodbc.so

/u01/app/oracle/product/fmw/Oracle_BI1/bifoundation/odbc/lib
/u01/app/oracle/product/TimesTen/tt1122/lib
/u01/app/oracle/product/fmw/Oracle_BI1/common/ODBC/Merant/7.1.5/lib
/u01/app/oracle/product/fmw/Oracle_BI1/bifoundation/odbc/lib
/u01/app/oracle/product/TimesTen/tt1122/lib
/u01/app/oracle/product/fmw/Oracle_BI1/common/ODBC/Merant/7.1.5/lib

Documentation / Reference

• Why LD_LIBRARY_PATH is bad
• Dynamically Linked Libraries
• When should I set LD_LIBRARY_PATH? The short answer is never.