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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.
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.
TMPDIR is the canonical environment variable in Unix and POSIX [1] that should be used to specify a temporary directory for scratch space.Most Unix programs will honor this setting and use its value to denote the scratch area for temporary files instead of the common default of /tmp [2] [3] or /var/tmp.
PATH is an environment variable on Unix-like operating systems, DOS, OS/2, and Microsoft Windows, specifying a set of directories where executable programs are located. In general, each executing process or user session has its own PATH setting.
Multics had a pwd command (which was a short name of the print_wdir command) [11] from which the Unix pwd command originated. [12] The command is a shell builtin in most Unix shells such as Bourne shell, ash, bash, ksh, and zsh. It can be implemented easily with the POSIX C functions getcwd() or getwd().
The C shell implements both shell and environment variables. [14] Environment variables, created using the setenv statement, are always simple strings, passed to any child processes, which retrieve these variables via the envp[] argument to main(). Shell variables, created using the set or @ statements, are internal to C shell. They are not ...
Also, the current setting is reflected also in the built-in help screens. [20] Some versions of DR-DOS COMMAND.COM also support a PROMPT token $/ to display the current setting. COMMAND.COM since DR-DOS 7.02 also provides a pseudo-environment variable named %/% to allow portable batchjobs to be written.
In keeping with Unix shell conventions, Bash incorporates a rich set of features. The keywords, syntax, dynamically scoped variables, and other basic features of the language are all copied from the Bourne shell, sh. Other features, e.g., history, are copied from the C shell, csh, and the Korn Shell, ksh. It is a POSIX-compliant shell with ...