envf

envf runs a program with modified environment variables. 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
HOME=/home/user
NAME=VALUE
PATH=/usr/bin:/bin
...

For full usage documentation, see the output of envf --help. envf supports the -i option from POSIX env as well as the -0 and -u extensions that are present on GNU and FreeBSD.

Although envf follows many of the behavior and options from POSIX env and its implementations, it is not fully compatible. For example, envf quotes problematic variable names and values when printing them.

$ env -i NAME1=VALUE1 $'NAME2=\nVALUE2' 'NAME3="VALUE3"'
NAME1=VALUE1
NAME2=
VALUE2
NAME3="VALUE3"

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

Building & testing

To build envf, you need a Rust toolchain; see the rust-version field in Cargo.toml for the minimum version. Then run cargo build --release to produce an envf executable in target/release.

To test envf, you also need Python and pytest. Then run cargo test && pytest test.py.

Contributing

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