Project-Level .ackrc Files

Ack is a fantastic (and portable!) replacement for grep. It's aimed at programmers and by default will only search a white-list of known file-extensions so that it will only search the "code" in a directory.

ack looks at your ~/.ackrc file to get any customized "default" settings you want. I use my (user-level) ~/.ackrc to enable some personalized default options, e.g. color-ize output, always use a $PAGER, sort the output by filename, etc.

But sometimes I want to have directory-level (or project-level) additional settings, namely to always exclude/ignore certain directories when searching at the project-level.

For example, here are the exclusions I want for my Octopress build environment:

--ignore-dir=.gist-cache
--ignore-dir=.pygments-cache
--ignore-dir=.sass-cache
--ignore-dir=.themes
--ignore-dir=\_deploy
--ignore-dir=public

So, I wrote-up a little ack wrapper script: ack-wrapper. It crawls the directory tree looking for an additional "local" .ackrc file, starting from the current working directory crawling up through any parent directories until we find a .ackrc file (or until we reach either $HOME or /).

(Update 2012-03-10: It looks like Ack v2.0 supports PWD .ackrc files natively, and has some other neat enhancements to boot!)

#!/bin/sh
# Wrapper around 'ack' to crawl all directories from `pwd` to / (or $HOME)
# looking for a "local" .ackrc file. Useful for setting project-level
# --ignore-dir settings.
 
# Search for "local" .ackrc file in CWD or any parents
HOME=~
ackrc=""
match=""
dir=$(pwd)
while [ "${dir}" != "/" -a "${match}" = "" ]; do
    if [ -e "${dir}/.ackrc" ]; then
        if [ "${dir}" != "${HOME}" ]; then
            match=1
            echo "(Include: ${dir}/.ackrc)"
            ackrc=$(egrep "^[^#]" "${dir}/.ackrc" | tr '\n' ' ')
        else
            match=0
        fi
    else
        dir=$(dirname "${dir}")
    fi
done
 
# Add quote-wrapping for any additional args to ensure proper passing to
# real 'ack'.
for arg in "$@"; do
    if [ -z "${ackrc}" ]; then
        ackrc="'${arg}'"
    else
        ackrc="${ackrc} '${arg}'"
    fi
done
 
# Build command to eval
cmd="command ack ${ackrc}"
if [ ! -t 0 ]; then
    # If stdin is a pipe, use cat to redirect stdin to stdout and pipe
    # that data into ack.
    cmd="cat | ${cmd}"
fi
 
# Eval the final command
eval "${cmd}"

Usage

• Grab the latest version of the ack-wrapper script, drop it somewhere in your $PATH (I like having a ~/bin/ directory), and make sure it's executable (chmod 755 path/to/ack-wrapper).
• Update your .bashrc to alias ack=ack-wrapper, so that running ack ... will first call the wrapper script, search for any "local" .ackrc files, insert any additional options found into the original supplied command-line arguments, and finally call the (real) ack executable.