env Command
Beginner Shell Scripting man(1)Display or set environment variables
👁 145 views
📅 Updated: Apr 28, 2026
SYNTAX
env [OPTION]... [NAME=VALUE]... [COMMAND]
What Does env Do?
env displays environment variables or runs a command with a modified environment. Without arguments, it prints all current environment variables. With arguments, it sets variables for a single command execution.
env is useful for running commands with specific environment settings without modifying the current shell, finding the correct interpreter in scripts (#!/usr/bin/env python3), and debugging environment issues.
The #!/usr/bin/env python3 pattern in script shebangs is widely used because it finds the python3 executable in the user's PATH, making scripts more portable across different systems.
env is useful for running commands with specific environment settings without modifying the current shell, finding the correct interpreter in scripts (#!/usr/bin/env python3), and debugging environment issues.
The #!/usr/bin/env python3 pattern in script shebangs is widely used because it finds the python3 executable in the user's PATH, making scripts more portable across different systems.
Options & Flags
| Option | Description | Example |
|---|---|---|
| -i | Start with empty environment | env -i PATH=/usr/bin bash |
| -u | Unset a variable | env -u HTTP_PROXY curl https://example.com |
| VAR=val | Set variable for the command | env NODE_ENV=production node app.js |
| (no args) | Print all environment variables | env |
| -0 | End each line with NUL instead of newline | env -0 | sort -z |
| #!/usr/bin/env | Find interpreter in PATH (shebang) | #!/usr/bin/env python3 |
Practical Examples
#1 Show all variables
Displays all current environment variables.
$ env
Output:
HOME=/home/user\nPATH=/usr/bin:/bin\nSHELL=/bin/bash
#2 Run with custom environment
Runs node with NODE_ENV set to production, without affecting the current shell.
$ env NODE_ENV=production node server.js#3 Run with empty environment
Starts a command with minimal environment variables.
$ env -i HOME=$HOME PATH=/usr/bin bash -c "echo clean shell"#4 Unset variable for command
Runs curl without the http_proxy variable (bypasses proxy).
$ env -u http_proxy curl https://api.example.com#5 Sort environment variables
Displays all variables in alphabetical order.
$ env | sort#6 Portable shebang
Used in script first line to find python3 in the user's PATH.
$ #!/usr/bin/env python3Tips & Best Practices
#!/usr/bin/env for scripts: Use #!/usr/bin/env python3 instead of #!/usr/bin/python3 in scripts. env finds the right interpreter regardless of where it is installed.
env vs printenv: env without args and printenv both show environment variables. env can also run commands; printenv can show a single variable: printenv HOME.
env -i is very minimal: env -i strips ALL variables. Most programs need at least HOME, PATH, and TERM to function properly.
Frequently Asked Questions
How do I set a variable for a single command?
Use env VAR=value command or simply VAR=value command. The variable only exists for that command.
What does #!/usr/bin/env do?
In script shebangs, env searches PATH for the specified interpreter. This is more portable than hard-coding the path.
How do I clear all environment variables?
Use env -i command to run a command with an empty environment. Add specific variables: env -i PATH=/usr/bin HOME=$HOME command.
Related Commands
More Shell Scripting Commands
Download Shell Scripting Cheat Sheet
View all 31 Linux command cheat sheets →Master Linux with Professional eBooks
Curated IT eBooks covering Linux, DevOps, Cloud, and more
Browse Books →