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The Silver Searcher

An attempt to make something better than ack, which itself is better than grep.

Why use Ag?

  • It searches through code about 3x-5x faster than Ack.
  • It ignores files matched by patterns in your .gitignore and .hgignore.
  • If there are files in your source repo that you don't want to search, just add their patterns to a .agignore file. *cough* extern *cough*
  • The binary name is 33% shorter than Ack!

How is it so fast?

  • Searching for literals (no regex) uses Boyer-Moore-Horspool strstr.
  • Files are mmap()ed instead of read into a buffer.
  • If you're building with PCRE 8.21 or greater, regex searches use the JIT compiler.
  • Ag calls pcre_study() before executing the regex on a jillion files.
  • Instead of calling fnmatch() on every pattern in your ignore files, non-regex patterns are loaded into an array and binary searched.
  • Ag uses Pthreads to take advantage of multiple CPU cores and search files in parallel.

This blog post gives an idea of how I go about improving performance.

Installation

Ubuntu 12.04+:

Add the PPA. Make sure you have python-software-properties installed, then:

sudo add-apt-repository ppa:ggreer/ag
sudo apt-get update
sudo apt-get install the-silver-searcher

If you get the error -bash: /usr/bin/ag: No such file or directory, congratulations, you are one of the lucky few. Apt managed to install the i386 version of Ag on an x86-64 system. I have no idea why this happens. To fix this issue, you'll have to apt-get install ia32-libs or apt-get purge the-silver-searcher and build from source.

Gentoo:

emerge the_silver_searcher

OS X:

brew install the_silver_searcher

For debs, rpms, and static builds, see the downloads page.

Building from source

  1. Install dependencies (Automake, pkg-config, PCRE):
    • Ubuntu: apt-get install -y automake pkg-config libpcre3-dev
    • OS X: Install homebrew, then brew install automake pkg-config pcre
    • FreeBSD: Install automake using ports: cd /usr/ports/devel/automake && make install ...then install dependencies with pkg_add: pkg_add -r pkg-config pcre
    • Windows: It's complicated. See this wiki page.
  2. Run the build script (which just runs aclocal, automake, etc):
    • ./build.sh
  3. Make install:
    • sudo make install

Current development status

It's quite stable now. Most changes are new features, minor bug fixes, or performance improvements. It's much faster than Ack in my benchmarks.

ack blahblahblah ~/code  6.59s user 1.94s system 99% cpu 8.547 total

ag blahblahblah ~/code  1.39s user 1.81s system 229% cpu 1.396 total

You can use Ag with my fork of the popular ackmate plugin, which lets you use both Ack and Ag for searching in Textmate. You can also move or delete "~/Library/Application Support/TextMate/PlugIns/AckMate.tmplugin/Contents/Resources/ackmate_ack" and run ln -s /usr/local/bin/ag "~/Library/Application Support/TextMate/PlugIns/AckMate.tmplugin/Contents/Resources/ackmate_ack"

You can use Ag with ack.vim by adding the following line to your .vimrc:

let g:ackprg = 'ag --nogroup --nocolor --column'

TODO

A special thanks goes out to Alex Davies. He has given me some excellent recommendations to improve Ag. Many of these things are still on my list:

  • Optimizations
    • Profile read() against mmap(). Remember that's read() not fread().
    • Write a benchmarking script that tweaks various settings to find what's fastest.
  • Features
    • Symlink loop detection.
    • Behave better when matching in files with really long lines.
      • Report "match found at position X of line N" if line is > 10k chars.
  • Windows support
    • readdir() and stat() are much slower on Windows. Use FindNextFile() instead.
    • Support Visual Studio instead of autotools?
    • Need to use pthreads-win32 or something similar.

Other stuff you might like

  • Ack - Better than grep
  • AckMate - An ack-powered replacement for TextMate's slow built-in search.
  • ack.vim
  • Exuberant Ctags - Faster than Ag, but it builds an index beforehand. Good for really big codebases.
  • Git-grep - As fast as Ag but only works on git repos.