Env: Difference between revisions
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=Overview= | =Overview= | ||
Run a command with a modified environment. | Run a command with a modified environment, or just [[#No_Argument_Use|print the environment if no argument is provided]]. | ||
/usr/bin/env [''utility''] | /usr/bin/env [''utility''] | ||
/usr/bin/env bash | /usr/bin/env bash | ||
=Options= | |||
==<tt>-u</tt>== | |||
If the environment variable whose name follows <code>-u</code> is in the environment, remove it before processing the remaining options. The value for name must not include the ‘=’ character. | |||
==<tt>-i</tt>== | |||
Execute the command with only those environment variables specified by <code>name=value</code> options. The environment inherited by <code>env</code> is ignored completely. | |||
=No Argument Use= | |||
Displays environment values. | |||
=Modify the Environment to Run a Command= | |||
<syntaxhighlight lang='bash'> | |||
env SOME_VAR='some value' printenv | |||
</syntaxhighlight> | |||
will display, among other environment variables, SOME_VAR. | |||
==Use <tt>env</tt> to Dynamically Modify <tt>PATH</tt>== | |||
<syntaxhighlight lang='bash'> | |||
python --version # returns one version | |||
env PATH=/tmp/some-venv:${PATH} python --version # returns a different version | |||
</syntaxhighlight> | |||
=Use on the Shebang Line= | =Use on the Shebang Line= | ||
{{External|https://www.baeldung.com/linux/bash-shebang-lines}} | {{External|https://www.baeldung.com/linux/bash-shebang-lines}} | ||
The <code>env</code> command works by instructing the system to look for the specified interpreter through the <code>PATH</code> variable and use the first occurrence found. | |||
Latest revision as of 02:07, 20 February 2024
External
Internal
Overview
Run a command with a modified environment, or just print the environment if no argument is provided.
/usr/bin/env [utility]
/usr/bin/env bash
Options
-u
If the environment variable whose name follows -u is in the environment, remove it before processing the remaining options. The value for name must not include the ‘=’ character.
-i
Execute the command with only those environment variables specified by name=value options. The environment inherited by env is ignored completely.
No Argument Use
Displays environment values.
Modify the Environment to Run a Command
env SOME_VAR='some value' printenv
will display, among other environment variables, SOME_VAR.
Use env to Dynamically Modify PATH
python --version # returns one version
env PATH=/tmp/some-venv:${PATH} python --version # returns a different version
Use on the Shebang Line
The env command works by instructing the system to look for the specified interpreter through the PATH variable and use the first occurrence found.