Environmental variables and PATH

These variables are important for executing scripts written in Python, not for writing them. If they are not configured, the location of the Python binary has to be referenced by its fully qualified path location. As an example, here is the execution of a Python script without the environmental variable being declared in Windows:

C:\Python27\python wargames_print.py

The following is the equivalent in Linux or Unix if the reference to the proper interpreter is not listed at the top of the script and the file is in your current directory:

/usr/bin/python ./wargames_print.py

In Windows, if the environmental variable is set, you can simply execute the script by typing python and the script name. In Linux and Unix, we add a line at the top of the script to make it more portable. A benefit to us (penetration testers) is that this makes the script useful on many different types of systems, including Windows. This line is ignored by the Windows operating system natively, as it is treated as a comment. The following referenced line should be included at the top of all Python scripts:

#!/usr/bin/env python

This line lets the operating system determine the correct interpreter to run based on what is set in the PATH environmental variable. In many script examples on the Internet, you may see a direct reference to an interpreter, such as /usr/bin/python. This not considered good practice as it makes the code less portable and more prone to errors with potential system changes.