sed-rs

A GNU-compatible sed implementation in Rust, built on the foundations of sd.

sd is an excellent modern find-and-replace tool, but it intentionally breaks from traditional sed syntax. sed-rs takes the opposite approach: it adapts sd's fast Rust regex engine and atomic file-write strategy into a tool that speaks fluent GNU sed, so it can serve as a drop-in replacement in scripts, pipelines, and anywhere else GNU sed is expected.

Why

• You want sed but compiled from Rust with no C dependencies.
• You want consistent, modern regex syntax (Rust/PCRE-style ERE) without the BRE/ERE confusion of traditional sed.
• You want a sed you can also call as a Rust library.

Install

cargo install sed-rs

Or build from source:

git clone https://github.com/pegasusheavy/sed-rs.git
cd sed-rs
cargo build --release
# binary is at target/release/sed

Usage

sed-rs aims to accept the same flags and scripting language as GNU sed:

# simple substitution
echo 'hello world' | sed 's/world/rust/'

# in-place editing with backup
sed -i.bak 's/foo/bar/g' file.txt

# multiple expressions
sed -e '2d' -e 's/old/new/' input.txt

# script file
sed -f commands.sed input.txt

# quiet mode — only print explicit `p` output
sed -n '/pattern/p' file.txt

Supported flags

Flag	Description
-n, --quiet, --silent	Suppress automatic printing of pattern space
-e SCRIPT, --expression=SCRIPT	Add script commands
-f FILE, --file=FILE	Read script from file
-i[SUFFIX], --in-place[=SUFFIX]	Edit files in place (backup if SUFFIX given)
-E, -r, --regexp-extended	Accepted for compatibility (ERE is always on)
-s, --separate	Treat files as separate streams
-z, --null-data	NUL-delimited input/output

Supported commands

s, d, p, P, q, Q, a, i, c, y, =, l, z, n, N, D, h, H, g, G, x, b, t, T, :, r, w, {...}

Addressing: line numbers, $ (last line), /regex/, first~step, ranges (addr1,addr2), and negation (!).

Library

sed-rs also exports a Rust library so you can use sed scripting from your own code:

// One-shot convenience function
let output = sed_rs::eval("s/hello/world/", "hello there\n").unwrap();
assert_eq!(output, "world there\n");

// Builder API with options
use sed_rs::Sed;

let mut sed = Sed::new("s/foo/bar/g").unwrap();
sed.quiet(true);

let output = sed.eval("foo foo\n").unwrap();
assert_eq!(output, "");  // quiet: nothing unless explicit `p`

// Streaming I/O
use sed_rs::Sed;
use std::io;

let sed = Sed::new("s/old/new/g").unwrap();
let input = b"old old old\n";
let mut output = Vec::new();
sed.eval_stream(&input[..], &mut output).unwrap();
assert_eq!(String::from_utf8(output).unwrap(), "new new new\n");

Regex dialect

sed-rs always uses the Rust regex crate, which provides syntax similar to PCRE / ERE. The -E and -r flags are accepted for compatibility but are no-ops since extended syntax is the default. Traditional BRE-only constructs (e.g. \( for grouping) are not supported — use ( directly.

Acknowledgements

This project is built on ideas and code adapted from sd by Gregory, licensed under the MIT License. Specifically, sed-rs draws from sd's approach to regex replacement mapping, escape-sequence handling, and atomic file writes. See LICENSE-MIT for full attribution.

License

Licensed under either of

• Apache License, Version 2.0
• MIT License

at your option.

Copyright (c) 2026 Pegasus Heavy Industries LLC