env

Show the environment

$ env

$ env [program]

$ env [[-i|--ignore-environment]] [program]

$ env [[-u|--unset]] [variable] [program]

$ env [variable]=[value] [program]

$ env [variable1=value variable2=value variable3=value ...] [program]

env [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]

-i, --ignore-environment
    Start with an empty environment.

-u, --unset=NAME
    Remove the variable named NAME from the environment.

-0, --null
    end each output line with NUL, not newline

--help
    Display help message and exit.

--version
    Output version information and exit.

NAME=VALUE
    Set the environment variable NAME to VALUE.

COMMAND [ARG]...
    Execute COMMAND with the modified environment. If no COMMAND is given, print the current environment.

-
    After this option, no further option processing occurs. Any remaining arguments are interpreted directly as command names, which allows you to pass options to the command without them being interpreted as env options.

The env command is a fundamental utility in Linux used to view, modify, and execute programs within a custom environment. It allows users to inspect the current environment variables, set new variables for a specific command invocation, or even clear the entire environment before executing a program. The command's primary function is to manage the set of key-value pairs that influence the behavior of processes, such as the search path for executables (PATH), the terminal type (TERM), and user-specific configurations. It is particularly useful for creating isolated environments or for running programs with different configurations than the default system settings. Understanding env is essential for effective scripting and managing software dependencies. Its simplicity hides a powerful ability to customize the execution context of applications.

Some systems may impose limits on the total size of the environment, potentially leading to errors if you set too many variables or variables that are too large. Also be aware that the `env` command only affects the environment of the specified command and its child processes. It does not permanently alter the user's shell environment.

env by itself lists the current environment variables.
env -i COMMAND executes COMMAND with an empty environment.
env NAME=VALUE COMMAND executes COMMAND with NAME set to VALUE.
env -u NAME COMMAND executes COMMAND without NAME in environment.

The `env` command has been a standard part of Unix-like operating systems for many years, appearing in early versions of POSIX.
Its initial purpose was to provide a way to isolate and control the environment in which commands are executed, which is useful for scripting, testing, and managing application dependencies. Over time, its functionality has remained largely consistent, focusing on the core ability to manipulate environment variables.

set(1), export(1), printenv(1)