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env is a shell command for Unix and Unix-like operating systems. It is used to either print a list of environment variables or run another utility in an altered environment without having to modify the currently existing environment. Using env, variables may be added or removed, and existing variables may be changed by assigning new values to them.
For this reason, libc unsets these environment variables at startup in a setuid process. setuid programs usually unset unknown environment variables and check others or set them to reasonable values. In general, the collection of environment variables function as an associative array where both the keys and values are strings. The ...
On DOS, OS/2, and Windows operating systems, the %PATH% variable is specified as a list of one or more directory names separated by semicolon (;) characters. [5]The Windows system directory (typically C:\WINDOWS\system32) is typically the first directory in the path, followed by many (but not all) of the directories for installed software packages.
#! /usr/bin/env python3 – Execute with a Python interpreter, using the env program search path to find it #! /bin/false – Do nothing, but return a non-zero exit status , indicating failure. Used to prevent stand-alone execution of a script file intended for execution in a specific context, such as by the . command from sh/bash, source from ...
Environment variables are a facility provided by some operating systems.Within the OS's shell (ksh in Unix, bash in Linux, COMMAND.COM in DOS and CMD.EXE in Windows) they are a kind of variable: for instance, in unix and related systems an ordinary variable becomes an environment variable when the export keyword is used.
In Python, if a name is intended to be "private", it is prefixed by one or two underscores. Private variables are enforced in Python only by convention. Names can also be suffixed with an underscore to prevent conflict with Python keywords. Prefixing with double underscores changes behaviour in classes with regard to name mangling.
Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
IDLE (short for Integrated Development and Learning Environment) [2] [3] is an integrated development environment for Python, which has been bundled with the default implementation of the language since 1.5.2b1. [4] [5] It is packaged as an optional part of the Python packaging with many Linux distributions.