variables

Overview of important variables

$PATH

What is $PATH?

$PATH is an environmental variable in Linux and Unix-like operating systems which specifies directories that hold executable programs. When the user runs any command in the terminal, it searches for executable files with the help of the PATH Variable in response to commands executed by a user.

It is very simple to view the Path of the relevant user with help of the command "echo $PATH".

$PATH

# example when using echo $PATH
user4@polobox:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

$LD_LIBRARY_PATH

LD_LIBRARY_PATH provides a list of directories where shared libraries are searched for first.

LD_LIBRARY_PATH is the predefined environmental variable in Linux/Unix which sets the path which the linker should look in to while linking dynamic libraries/shared libraries.

LD_LIBRARY_PATH contains a colon separated list of paths and the linker gives priority to these paths over the standard library paths /lib and /usr/lib. The standard paths will still be searched, but only after the list of paths in LD_LIBRARY_PATH has been exhausted.

The best way to use LD_LIBRARY_PATH is to set it on the command line or script immediately before executing the program. This way the new LD_LIBRARY_PATH isolated from the rest of your system

$LD_PRELOAD

LD_PRELOAD loads a shared object before any others when a program is run

If you set LD_PRELOAD to the path of a shared object, that file will be loaded before any other library Read more: https://blog.fpmurphy.com/2012/09/all-about-ld_preload.html#ixzz6rx8UeNvh

References

• https://tryhackme.com/room/linuxprivesc (Task 7 - $LD_LIBRARY_PATH, $LD_PRELOAD)