Crate grep_searcher

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This crate provides an implementation of line oriented search, with optional support for multi-line search.

Brief overview

The principle type in this crate is a Searcher, which can be configured and built by a SearcherBuilder. A Searcher is responsible for reading bytes from a source (e.g., a file), executing a search of those bytes using a Matcher (e.g., a regex) and then reporting the results of that search to a Sink (e.g., stdout). The Searcher itself is principally responsible for managing the consumption of bytes from a source and applying a Matcher over those bytes in an efficient way. The Searcher is also responsible for inverting a search, counting lines, reporting contextual lines, detecting binary data and even deciding whether or not to use memory maps.

A Matcher (which is defined in the grep-matcher crate) is a trait for describing the lowest levels of pattern search in a generic way. The interface itself is very similar to the interface of a regular expression. For example, the grep-regex crate provides an implementation of the Matcher trait using Rust’s regex crate.

Finally, a Sink describes how callers receive search results producer by a Searcher. This includes routines that are called at the beginning and end of a search, in addition to routines that are called when matching or contextual lines are found by the Searcher. Implementations of Sink can be trivially simple, or extraordinarily complex, such as the Standard printer found in the grep-printer crate, which effectively implements grep-like output. This crate also provides convenience Sink implementations in the sinks sub-module for easy searching with closures.


This example shows how to execute the searcher and read the search results using the UTF8 implementation of Sink.

use {

const SHERLOCK: &'static [u8] = b"\
For the Doctor Watsons of this world, as opposed to the Sherlock
Holmeses, success in the province of detective work must always
be, to a very large extent, the result of luck. Sherlock Holmes
can extract a clew from a wisp of straw or a flake of cigar ash;
but Doctor Watson has to have it taken out for him and dusted,
and exhibited clearly, with a label attached.

let matcher = RegexMatcher::new(r"Doctor \w+")?;
let mut matches: Vec<(u64, String)> = vec![];
Searcher::new().search_slice(&matcher, SHERLOCK, UTF8(|lnum, line| {
    // We are guaranteed to find a match, so the unwrap is OK.
    let mymatch = matcher.find(line.as_bytes())?.unwrap();
    matches.push((lnum, line[mymatch].to_string()));

assert_eq!(matches.len(), 2);
    (1, "Doctor Watsons".to_string())
    (5, "Doctor Watson".to_string())

See also examples/ from the root of this crate’s directory to see a similar example that accepts a pattern on the command line and searches stdin.


  • A collection of convenience implementations of Sink.


  • The behavior of binary detection while searching.
  • An encoding to use when searching.
  • An iterator over lines in a particular slice of bytes.
  • An explicit iterator over lines in a particular slice of bytes.
  • Controls the strategy used for determining when to use memory maps.
  • A searcher executes searches over a haystack and writes results to a caller provided sink.
  • A builder for configuring a searcher.
  • A type that describes a contextual line reported by a searcher.
  • Summary data reported at the end of a search.
  • A type that describes a match reported by a searcher.



  • A trait that defines how results from searchers are handled.
  • A trait that describes errors that can be reported by searchers and implementations of Sink.