Searching across a project's codebase for keywords is a pretty standard
requirement when starting something new. Recently I inherited a very large
Rails app with 238 models and 348 controllers. That is to say nothing of
etc. It was pretty clear that I was going to have to find a way to explore
certain parts of the code by looking for what I was working on that day in
Lots of editors have this capability built in including: RubyMine, Sublime
Text, Atom, and Textmate, but at Headway we use console Vim inside of Tmux for
the majority of our development, and project-wide search isn't provided out of
the box. This led me to try several different "grep like" tools over the years,
including just plain [grep](https://en.wikipedia.org/wiki/Grep). However, with
thousands of files to search through, I needed speed. For many years I was
happily served by a tool called [Ack](http://beyondgrep.com/documentation/),
which bills itself as a much faster grep replacement. But even with all the
improvements over vanilla grep that Ack made, it was still too slow for my
needs. Enter [The Silver
Searcher](https://github.com/ggreer/the_silver_searcher), or "Ag" as it's
Ag starts out claiming that "it is an order of magnitude faster than ack".
A bold statement to be sure, but I can say with certainty that it is
indeed worth the upgrade.
## Installing Ag
To install Ag, use [homebrew](http://brew.sh/): `brew install
the_silver_searcher`. For other platforms, see the
## Configuring Ag To Ignore Directories
Without any configuration, Ag will search through all the files in
a directory except for those matched by ignore patterns specified in
the project's `.gitignore` or `.hgignore` or `.agignore` files. You can
also create a `~/.agignore` file at the root of your home directory for
Ignoring some directories in a Rails app like `/public/system` and
`/coverage` that aren't typically found in the `.gitignore`, can have
a dramatic impact on the speed at which results are returned from Ag.
Without a tuned `.agignore`, in the project I mentioned earlier, Ag would
take 15 seconds to return results. With a tuned `.agignore` file though,
I was able to get results back in under a second! Ack or grep were
unusable and just locked up my machine.
The `.agignore` pattern is really straightforward. You simply list the
folders or files you want to ignore by name like so:
-- CODE line-numbers language-lang --
## Performing Advanced Searches
One of the tasks that I needed to perform involved deleting a whole workflow
from the app. This meant that while I wanted to delete code that included text
like "news" I didn't want to include text like "newsignword". In order to find
only items that stopped after the four characters "news" I needed to use
a negative lookahead regex.
Ag uses Perl-Compatible Regular Expression (PCRE) syntax, which I wasn't
overly familiar with, so here are a few sites that I used to help test my
I ended up with this:
-- CODE line-numbers language-lang --
This would search for the string "news" but omit results that would
include "ignword" or "tyle" immediately following "news". So while all the
"news" hits showed up, I was able to filter out tens of hits for
"newsignword" and "newStyle".
## Wrap up
Next time you need to get up to speed quickly on a new codebase, give Ag
a shot! Coupled with other tools like [ctags](http://ctags.sourceforge.net/),
and [rails.vim](https://github.com/tpope/vim-rails), [Vim](http://www.vim.org/)
is a great IDE for Ruby on Rails development! Also, check out the cool things
happening in the [neovim](https://neovim.io/) space!
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