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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.
A special system-wide environment variable found on Windows NT and its derivatives. Its value is the location of the current user's profile directory, in which is found that user's HKCU registry hive (NTUSER). Users can also use the %USERNAME% variable to determine the active users login identification.
Bash can execute the vast majority of Bourne shell scripts without modification, with the exception of Bourne shell scripts stumbling into fringe syntax behavior interpreted differently in Bash or attempting to run a system command matching a newer Bash builtin, etc. Bash command syntax includes ideas drawn from the Korn Shell (ksh) and the C ...
POSIX shells set the following environment variables while using the cd command: [22] OLDPWD The previous working directory (as set by the cd command). PWD The current working directory (as set by the cd command).
In the DOS era, it was customary to add a PATH {program directory}; %PATH% or SET PATH = {program directory}; %PATH% line to AUTOEXEC.BAT. When a command is entered in a command shell or a system call is made by a program to execute a program, the system first searches the current working directory and then searches the path, examining each ...
Command-line shells provide a command-line interface (CLI) to the operating system, while graphical shells provide a graphical user interface (GUI). Other possibilities, although not so common, include a voice user interface and various implementations of a text-based user interface (TUI) that are not CLI, such as text-based menu systems.
Shell functions, especially if the command being created needs to modify the internal runtime environment of the shell itself (such as environment variables), needs to change the shell's current working directory, or must be implemented in a way which guarantees they it appear in the command search path for anything but an interactive shell ...
One example of this is Bash, which offers the same grammar and syntax as the Bourne shell, and which also provides a POSIX-compliant mode. [13] As such, most shell scripts written for the Bourne shell can be run in BASH, but the reverse may not be true since BASH has extensions which are not present in the Bourne shell.