Linux env#

env command#


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

Options of env command

  1. Without any argument: print out a list of all environment variables

    • Syntax: env

  2. -i or –ignore-environment or only –: runs a command with an empty environment

    • Syntax: env -i your_command

    • Example: env -i /bin/sh

  3. -u or –unset: remove variable from the environment

    • Syntax: env -u variable_name

  4. -0 or –null: End each output line with NULL, not newline

    • Syntax: env -0

  5. –version: Display version information and exit

    • Syntax: env --version

  6. –help: Display a help message and exit

    • Syntax: env --help

Environment Variables#

To set a global ENV#

$ export NAME=Value
$ set NAME=Value

To set a local ENV#

$ NAME=Value

To set user wide ENVs#

~/.bashrc, ~/.bash_profile, ~/.bash_login, ~/.profile

$ sudo vi ~/.bashrc
export NAME=Value
$ source ~/.bashrc

To set system wide ENVs#

/etc/environment, /etc/profile, /etc/profile.d/, /etc/bash

$ sudo -H vi /etc/environment

Unset environment variables#

$ unset NAME
$ NAME=''

Some commonly used ENVs in Linux#

$USER: Gives current user's name.
$PATH: Gives search path for commands.
$PWD: Gives the path of present working directory.
$HOME: Gives path of home directory.
$HOSTNAME: Gives name of the host.
$LANG: Gives the default system language.
$EDITOR: Gives default file editor.
$UID: Gives user ID of current user.
$SHELL: Gives location of current user's shell program.


echo $SHELL
echo $USER
echo $PATH
echo $PWD
echo $LANG
echo $HOME
echo $RANDOM