env

Run a command with a modified environment, or print the current environment. Use when setting environment variables for a single command, clearing the environment, or inspecting variables.

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85%

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env - Run a Command in a Modified Environment

Synopsis

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

Set each NAME to VALUE in the environment and run COMMAND. With no COMMAND, print the resulting environment.

Flags

Flag	Long Form	Description
-i	--ignore-environment	Start with an empty environment
-u	--unset=NAME	Remove variable NAME from the environment
-0	--null	End each output line with NUL, not newline
-C	--chdir=DIR	Change directory to DIR before running COMMAND
-S	--split-string=S	Process and split S into separate arguments
-v	--debug	Print verbose information for each processing step
	--default-signal[=SIG]	Reset handling of SIG to the default
	--ignore-signal[=SIG]	Set handling of SIG to do nothing
	--block-signal[=SIG]	Block delivery of SIG
	--list-signal-handling	List non-default signal handling to stderr
	--help	Display help
	--version	Output version

Examples

# Print all environment variables
env

# Run command with extra variable
env VAR=value command

# Run with multiple variables
env DB_HOST=localhost DB_PORT=5432 python app.py

# Run with empty environment
env -i /bin/bash

# Remove a variable for this command
env -u LD_PRELOAD command

# Change directory and run
env -C /tmp ls

# In shebangs with arguments (using -S)
#!/usr/bin/env -S python3 -u

# Print environment, NUL-separated (for parsing)
env -0

# Run with clean environment plus specific vars
env -i HOME="$HOME" PATH="$PATH" command

Gotchas

env is most commonly used in shebang lines: #!/usr/bin/env python3 which finds python3 in $PATH (more portable than hardcoding the path).
-S (split string) is needed in shebangs when passing arguments: #!/usr/bin/env -S python3 -u because the kernel passes the entire string after env as a single argument.
env -i gives a truly empty environment, which may break programs that depend on $HOME, $PATH, $TERM, etc.
env VAR=value command is equivalent to VAR=value command in most shells, but env works as a standalone binary (useful in shebangs and non-shell contexts).
Without COMMAND, env just prints the environment, which is equivalent to printenv.

Repository: flox/floxenvs
Commit: bb1f07d

Last updated: 5 days ago
Created: 5 days ago

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