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#!/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 ...
In Unix, Linux and other Unix-like operating systems, the first two bytes in a file can be the characters "#!", which constitute a magic number (hexadecimal 23 and 21, the ASCII values of "#" and "!") often referred to as shebang, prefix the first line in a script, with the remainder of the line being a command usually limited to a max of 14 ...
Alternatively, from command shells such as bash, a user can change environment variables for a particular command invocation by indirectly invoking it via env or using the ENVIRONMENT_VARIABLE=VALUE <command> notation. A running program can access the values of environment variables for configuration purposes.
The Unix "shebang" – #! – used on the first line of a script to point to the interpreter to be used. "Magic comments" identifying the encoding a source file is using, [21] e.g. Python's PEP 263. [22] The script below for a Unix-like system shows both of these uses:
However, for explicit licensing reasons with Catalina [69] (c.2019), Apple replaced its default shell, Bash version 3.2 (c.2006), with Z Shell version 5.7 (c.2019). [70] [71] "The bash binary bundled with macOS has been stuck on version 3.2 for a long time now. bash v4 was released in 2009 and bash v5 in January 2019. The reason Apple has not ...
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.
Tcl, Perl, Rexx, and Python have graphics toolkits and can be used to code functions and procedures for shell scripts which pose a speed bottleneck (C, Fortran, assembly language &c are much faster still) and to add functionality not available in the shell language such as sockets and other connectivity functions, heavy-duty text processing ...