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CLI interface

CLI flags

virtualenv is primarily a command line application.

It modifies the environment variables in a shell to create an isolated Python environment, so you'll need to have a shell to run it. You can type in virtualenv (name of the application) followed by flags that control its behaviour. All options have sensible defaults, and there's one required argument: then name/path of the virtual environment to create. The default values for the command line options can be overridden via the :ref:`conf_file` or :ref:`env_vars`. Environment variables takes priority over the configuration file values (--help will show if a default comes from the environment variable as the help message will end in this case with environment variables or the configuration file).

The options that can be passed to virtualenv, along with their default values and a short description are listed below.

:command:`virtualenv [OPTIONS]`

.. table_cli::
   :func: build_parser


Configuration file

virtualenv looks for a standard ini configuration file. The exact location depends on the operating system you're using, as determined by :pypi:`appdirs` application data definition. The configuration file location is printed as at the end of the output when --help is passed.

The keys of the settings are derived from the long command line option. For example, :option:`--python <python>` would be specified as:

python = /opt/python-3.3/bin/python

Options that take multiple values, like :option:`extra-search-dir` can be specified as:

extra-search-dir =

Environment Variables

Each command line option has a corresponding environment variables with the name format VIRTUALENV_<UPPER_NAME>. The UPPER_NAME is the name of the command line options capitalized and dashes ('-') replaced with underscores ('_').

For example, to use a custom Python binary, instead of the one virtualenv is run with, you can set the environment variable VIRTUALENV_PYTHON like:

env VIRTUALENV_PYTHON=/opt/python-3.8/bin/python virtualenv

This also works for appending command line options, like :option:`extra-search-dir`, where a literal newline is used to separate the values:

env VIRTUALENV_EXTRA_SEARCH_DIR="/path/to/dists\n/path/to/other/dists" virtualenv

The equivalent CLI-flags based invocation, for the above example, would be:

virtualenv --extra-search-dir=/path/to/dists --extra-search-dir=/path/to/other/dists
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