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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.
Shellshock, also known as Bashdoor, [1] is a family of security bugs [2] in the Unix Bash shell, the first of which was disclosed on 24 September 2014.Shellshock could enable an attacker to cause Bash to execute arbitrary commands and gain unauthorized access [3] to many Internet-facing services, such as web servers, that use Bash to process requests.
In all Unix and Unix-like systems, as well as on Windows, each process has its own separate set of environment variables.By default, when a process is created, it inherits a duplicate run-time environment of its parent process, except for explicit changes made by the parent when it creates the child.
Prints a command to the terminal as Bash reads it. Bash reads constructs all at once, such as compound commands which include if-fi and case-esac blocks. If a set -v is included within a compound command, then "verbose" will be enabled the next time Bash reads code as input, ie, after the end of the currently executing construct. [108]
#! /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 ...
For example, some would say that the use of an uninitialized variable's value in Java code is a syntax error, but many others would disagree [1] [2] ...
On many systems it was necessary to obtain control of environment settings, access a local file table, determine the intended data set, and handle hardware correctly in the case of a punch card reader, magnetic tape drive, disk drive, line printer, card punch, or interactive terminal.
Each window is represented by a character matrix. The programmer sets up the desired appearance of each window, then tells the curses package to update the screen. The library determines a minimal set of changes that are needed to update the display and then executes these using the terminal's specific capabilities and control sequences.