env

Show all environment variables

$ env

$ env VAR=value [command]

$ env -i [command]

$ env -u [VAR] [command]

env [options] [VAR=value]... [command]

env runs a program in a modified environment. It can display current environment variables, set new ones, unset existing ones, or run commands with a clean environment.
The command is useful for setting variables temporarily or debugging environment issues.

-i, --ignore-environment

Start with empty environment

Remove variable from environment

End lines with NUL, not newline

Change directory before running command

Process and split string into arguments

Shebang lines:

$ #!/usr/bin/env bash
#!/usr/bin/env python3
#!/usr/bin/env node

$ env NODE_ENV=production npm start
env DATABASE_URL=postgres://... rails console

$ env -i PATH="$PATH" command

$ env | grep PATH
env | sort

Variables shown as:

$ NAME=value
PATH=/usr/bin:/bin
HOME=/home/user

env

Runs command with modified environment

Sets variables for current shell and children

$ # env (one command only)
env VAR=value command

# export (persistent)
export VAR=value
command  # VAR is available

Variables set with env don't persist after command exits. Shell built-ins may not be accessible with env. PATH must be set for clean environment. Quotes needed for values with spaces. Different from the export shell built-in.

env has been part of Unix since the early days, included in POSIX standards for environment manipulation.

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