This crate currently needs the nightly toolchain. See the tracking issue for stabilization.

A Rust library (crate) that runs the cargo rustc --print cfg command and parses the output. This is inspired by the rustc-cfg crate, which runs the rustc --print cfg command and parses the output, but it does not take into account any flags or configurations passed from Cargo to the Rust compiler (rustc) when building a project using Cargo. For example, if the RUSTFLAGS environment variable is used to add a target feature, i.e. RUSTFLAGS="-C target-feature=+crt-static, then the rustc --print cfg command will not list the added target feature in its output because the RUSTFLAGS environment variable is managed by Cargo. However, the cargo rustc --print cfg will list the added target feature in its output. This crate is useful for developing third-party Cargo custom subcommands that need compiler configuration information. This crate is not recommended for build scripts.

Note, this crate currently needs the nightly toolchain.

use cargo_rustc_cfg;

let host = cargo_rustc_cfg::host()?;
println("{:?}", host);

Add the following to a package's manifest (Cargo.toml):

cargo-rustc-cfg = "0.3"

If using the Rust 2015 Edition, then also add the following to the lib.rs or main.rs source file:

extern crate cargo_rustc_cfg;

Tests are run using the cargo test command. Currently, only documentation tests are implemented because for a relatively simple, small library these provide enough coverage. If the default toolchain is stable but the nightly toolchain is installed, the cargo +nightly test command can be used without having to switch the default toolchain.

The cargo-rustc-cfg project is licensed under either the MIT license or the Apache 2.0 license. See the LICENSE-MIT or LICENSE-APACHE files for more information about licensing and copyright.