rustix

Safe Rust bindings to POSIX/Unix/Linux/Winsock2 syscalls

A Bytecode Alliance project

rustix provides efficient memory-safe and I/O-safe wrappers to POSIX-like, Unix-like, Linux, and Winsock2 syscall-like APIs, with configurable backends. It uses Rust references, slices, and return values instead of raw pointers, and io-lifetimes instead of raw file descriptors, providing memory safety, I/O safety, and provenance. It uses Results for reporting errors, bitflags instead of bare integer flags, an Arg trait with optimizations to efficiently accept any Rust string type, and several other efficient conveniences.

rustix is low-level and, and while the net API supports Winsock2 on Windows, the rest of the APIs do not support Windows; for higher-level and more portable APIs built on this functionality, see the cap-std, memfd, timerfd, and io-streams crates, for example.

rustix currently has two backends available:

• linux_raw, which uses raw Linux system calls and vDSO calls, and is supported on Linux on x86-64, x86, aarch64, riscv64gc, powerpc64le, arm (v5 onwards), mipsel, and mips64el, with stable, nightly, and 1.48 Rust.

  • By being implemented entirely in Rust, avoiding libc, errno, and pthread cancellation, and employing some specialized optimizations, most functions compile down to very efficient code. On nightly Rust, they can often be fully inlined into user code.
  • Most functions in linux_raw preserve memory, I/O safety, and pointer provenance all the way down to the syscalls.

• libc, which uses the libc crate which provides bindings to native libc libraries on Unix-family platforms, and windows-sys for Winsock2 on Windows, and is portable to many OS's.

The linux_raw backend is enabled by default on platforms which support it. To enable the libc backend instead, either enable the "use-libc" cargo feature, or set the RUSTFLAGS environment variable to --cfg=rustix_use_libc when building.

Cargo features

The modules rustix::io, rustix::fd, and rustix::ffi are enabled by default. The rest of the API is conditional with cargo feature flags:

Name	Description
fs	rustix::fs and rustix::path—Filesystem operations.
io_uring	rustix::io_uring—Linux io_uring.
mm	rustix::mm—Memory map operations.
net	rustix::net and rustix::path—Network-related operations.
param	rustix::param—Process parameters.
process	rustix::process—Process-associated operations.
rand	rustix::rand—Random-related operations.
termios	rustix::termios—Terminal I/O stream operations.
thread	rustix::thread—Thread-associated operations.
time	rustix::time—Time-related operations.
use-libc	Enable the libc backend.

Similar crates

rustix is similar to nix, simple_libc, unix, nc, and uapi. rustix is architected for I/O safety with most APIs using OwnedFd and AsFd to manipulate file descriptors rather than File or even c_int, and supporting multiple backends so that it can use direct syscalls while still being usable on all platforms libc supports. Like nix, rustix has an optimized and flexible filename argument mechanism that allows users to use a variety of string types, including non-UTF-8 string types.

relibc is a similar project which aims to be a full "libc", including C-compatible interfaces and higher-level C/POSIX standard-library functionality; rustix just aims to provide safe and idiomatic Rust interfaces to low-level syscalls. relibc also doesn't tend to support features not supported on Redox, such as *at functions like openat, which are important features for rustix.

rustix has its own code for making direct syscalls, similar to the sc and scall crates, though rustix can use either the Rust asm! macro or out-of-line .s files so it supports Rust versions from 1.48 through Nightly. rustix can also use Linux's vDSO mechanism to optimize Linux clock_gettime on all architectures, and all Linux system calls on x86. And rustix's syscalls report errors using an optimized Errno type.

rustix's *at functions are similar to the openat crate, but rustix provides them as free functions rather than associated functions of a Dir type. rustix's cwd() function exposes the special AT_FDCWD value in a safe way, so users don't need to open . to get a current-directory handle.

rustix's openat2 function is similar to the openat2 crate, but uses I/O safety types rather than RawFd. rustix does not provide dynamic feature detection, so users must handle the NOSYS error themselves.

rustix's termios module is similar to the termios crate, but uses I/O safety types rather than RawFd, and the flags parameters to functions such as tcsetattr are enums rather than bare integers. And, rustix calls its tcgetattr function tcgetattr, rather than Termios::from_fd.

Minimum Supported Rust Version (MSRV)

This crate currently works on the version of Rust on Debian stable, which is currently Rust 1.48. This policy may change in the future, in minor version releases, so users using a fixed version of Rust should pin to a specific version of this crate.