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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.
env: Displays and modifies environment variables: expr: Evaluates expressions factor: Factors numbers: false: Does nothing, but exits unsuccessfully groups: Prints the groups of which the user is a member hostid: Prints the numeric identifier for the current host id: Prints real or effective UID and GID: link: Creates a link to a file logname ...
Fish also includes feature-rich tab completion, with support for expanding file paths (with wildcards and brace expansion), environment variables, and command-specific completions. Command-specific completions, including options with descriptions, can be to some extent generated from the commands' man pages , but custom completions can also be ...
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 ...
Also, positional parameters as the argv array including argv[1], the $0 shell variable as argv[0], the Count of Indices parameter expansion $#var, the -d and -x operators of a testing syntax regarding directory and executability tests, respectively, the ! negate symbol, a looping construct in the foreach command, the set, echo and exit commands ...
A sophisticated shell can also change the environment in which other programs execute by passing named variables, a parameter list, or an input source. In Unix-like operating systems, users typically have many choices of command-line interpreters for interactive sessions.
e – An array of pointers to environment variables is explicitly passed to the new process image. l – Command-line arguments are passed individually (a l ist) to the function. p – Uses the PATH environment variable to find the file named in the file argument to be executed.
Shell variables, created using the set or @ statements, are internal to C shell. They are not passed to child processes. Shell variables can be either simple strings or arrays of strings. Some of the shell variables are predefined and used to control various internal C shell options, e.g., what should happen if a wildcard fails to match anything.