envf

envf runs a program with modified environment variables (and working directory). It is similar to Unix env but also supports reading from dotenv-style files.

The dotenv file parser currently used is dotenvy; please refer to its documentation for the file syntax.

envf project links: homepage, crates.io.

Usage

envf takes any number of NAME=VALUE environment variable definitions, followed by the program you wish to run and its arguments.

$ envf NAME=VALUE sh -c 'echo $NAME'
VALUE

To read from a dotenv/.env-style file, use the -f option followed by the file path. Unlike some similar programs, envf will not automatically read environment variables from .env files, because explicit is better than implicit.

$ echo NAME=VALUE > my-env

$ envf -f my-env sh -c 'echo $NAME'
VALUE

If run with no program specified, envf shows the environment variables that would be used if you were to specify a program.

$ envf NAME=VALUE
...
NAME=VALUE

For full usage documentation, see the envf manpage or the output of envf --help.

Compatibility

envf supports the -i option from POSIX env, as well as the -0, -C, and -u extensions that are present on GNU and FreeBSD.

Although envf mimics many of the behaviors and options of POSIX env (and some env implementations), it is not a compatible implementation and is not intended to be one.

The most visible difference is that envf quotes problematic variable names and values when printing them.

$ envf -i NAME1=VALUE1 $'NAME2=\nVALUE2' 'NAME3="VALUE3"'
NAME1=VALUE1
NAME2="\nVALUE2"
NAME3="\"VALUE3\""

In addition, envf permits specifying command-line options after variable definitions. This allows values specified in the command line to be overridden by those specified in a file.

$ echo NAME=VALUE2 > my-env

$ envf NAME=VALUE1 -f my-env sh -c 'echo $NAME'
VALUE2

Building and packaging

Building envf

Requires: Rust toolchain. See the rust-version field in Cargo.toml for the minimum version.

Run cargo build --release.

Generating the full license file

Requires: cargo-about.

Run cargo about generate -o target/LICENSE.html data/license-template.hbs.

Regenerating the --help message

This is only needed if you modify the manpage.

Requires: Python, groff.

Run tools/prerelease.py and then rebuild envf.

Testing

Requires: Python, pytest.

Run cargo test && pytest test.py.

Packaging

These are the files that you may want to include in the package:

• target/release/envf[.exe].
• target/LICENSE.html.
• envf.1.

Contributing

By contributing, you agree to license your contributions under the same license as this project (see the license field in Cargo.toml).