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Formula Cookbook
Making a formula is easy. Just brew create URL and then brew install FOO. If you want mxcl/master to merge your new formula then you should read the rest of this document because we want your formula to be awesome, and the cookbook will tell you how.
| Formula | The package description | /usr/local/Library/Formula/foo.rb |
| Keg | The installation prefix of a Formula | /usr/local/Cellar/foo/0.1 |
| Cellar | All kegs are installed in here | /usr/local/Cellar |
| Tap | An optional collection of Formulae | /usr/local/Library/Taps |
Did you see /usr/local/.git? Homebrew is built on Git (as long as you did brew update at least once). This means you can just do your work in /usr/local and merge in upstream updates as you go.
Homebrew installs to the Cellar, it then symlinks some of the installation into /usr/local so that other programs can see what’s going on. We suggest you ls a few of the kegs in your Cellar to see how it is all arranged.
Packages are installed according to their formulae, which live in /usr/local/Library/Formula. Check some out. You can view any formula at anytime with e.g. brew edit wget.
Ensure you’ve run brew update at least once ever before you start. This turns your Homebrew prefix into a Git repository. (Homebrew is built on top of Git. You did know that, right?)
Before contributing, make sure your package isn’t:
- already waiting to be merged (check the issue tracker)
- already isn’t in Homebrew (check
brew search foo) - isn’t in another Homebrew tap.
Make sure you search thoroughly (all aliases!) We don’t want you to waste your time.
Probably. But we have rules to keep the quality and goals of Homebrew intact: Please read Acceptable Formula.
Formulae aren’t that complicated. etl and browser are as simple as it gets.
And then Git and flac show more advanced functionality.
All you need to make a formula is a URL to the tarball.
brew create http://example.com/foo-0.1.tar.gz
This creates:
/usr/local/Library/Formula/foo.rb
And opens it in your $EDITOR. It’ll look like:
require 'formula'
class Foo < Formula
url 'http://example.com/foo-0.1.tar.gz'
homepage ''
md5 '1234567890ABCDEF1234567890ABCDEF'
# depends_on 'cmake'
def install
system "./configure", "--prefix=#{prefix}", "--disable-debug", "--disable-dependency-tracking"
# system "cmake", ".", *std_cmake_args
system "make install"
end
end
(Note: If brew said Warning: Version cannot be determined from URL when doing the create step, you’ll need to explicitly add the correct version to the formula with version 'foo' and then save the formula. brew install should then proceed without any trouble.)
We don’t accept formulae without homepages!
Homebrew doesn’t have a description field because the homepage is always up to date, and Homebrew is not. That’s way less maintenance for us. To satisfy the description, we’re going to invent a new packaging microformat and persuade everyone to publish it on their homepage. (where?)
brew install -i foo
You’re now at new prompt with the tarball extracted to a temporary sandbox.
Check the package’s README. Does the package install with autotools, cmake, or something else? Delete the commented out cmake lines if the package uses autotools (i.e. if it has a configure script).
The README probably tells you about dependencies. Homebrew or OS X probably already has them. You can check for Homebrew deps with brew search. These are the common deps that OS X comes with:
FreetypelibexpatlibGLlibiconvlibpcaplibpnglibxml2PythonRubyX11
There are plenty of others. Check /usr/lib, /usr/X11/lib to see.
We try to never duplicate libraries and complicated tools. We dupe some common tools (e.g. scons). But generally we avoid dupes because it’s one of Homebrew’s foundations. (And it causes build and usage problems!)
We encourage you to maintain your own fork with dupes as you require them.
Important: Since the introduction of superenv, `brew --prefix`/bin is NOT on the $PATH during formula installation. If you have dependencies at build time, you must specify them and brew will add them to the $PATH. You can test around this with `--env=std`.
class Foo < Formula depends_on 'jpeg' end
Note that you cannot (yet) depend on specific versions of a formula, or building with certain options. There is the concept of an optional dependency, but it’s not implemented yet (even though some formulae already sport them).
When you already have a lot of brews installed, its easy to miss a common dependency like glib or gettext.
You can double-check which libraries a binary links to with the otool command:
$ otool -L /usr/local/bin/ldapvi
/usr/local/bin/ldapvi:
/usr/lib/libssl.0.9.8.dylib (compatibility version 0.9.8, current version 0.9.8)
/usr/lib/libcrypto.0.9.8.dylib (compatibility version 0.9.8, current version 0.9.8)
/usr/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.3)
/usr/local/Cellar/glib/2.22.4/lib/libglib-2.0.0.dylib (compatibility version 2201.0.0, current version 2201.4.0)
/usr/local/Cellar/gettext/0.17/lib/libintl.8.dylib (compatibility version 9.0.0, current version 9.2.0)
/usr/local/Cellar/readline/6.0/lib/libreadline.6.0.dylib (compatibility version 6.0.0, current version 6.0.0)
/usr/local/Cellar/popt/1.15/lib/libpopt.0.dylib (compatibility version 1.0.0, current version 1.0.0)
/usr/lib/libncurses.5.4.dylib (compatibility version 5.4.0, current version 5.4.0)
/System/Library/Frameworks/LDAP.framework/Versions/A/LDAP (compatibility version 1.0.0, current version 2.2.0)
/usr/lib/libresolv.9.dylib (compatibility version 1.0.0, current version 38.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.0.0)
Homebrew doesn’t package the already-packaged. If your formula needs a gem or egg, you’ll need to check for these external dependencies:
class Foo < Formula
depends_on 'mg' => :ruby
depends_on 'json' => :python
end
Sometimes Python or Ruby package names don’t match the way that the dependency should be checked. For instance, Python’s `PyYAML` installs the package but its existence is checked with python -c " import yaml":
class Foo < Formula
depends_on LanguageModuleDependency.new :python, 'PyYAML', 'yaml'
end
Exit out of the interactive shell.
brew install -vd fooThe v is for verbose, the d debug. Debug mode dumps you to an interactive shell if the build fails so you can try to figure out what went wrong.
Check the top of the ./configure output (if applicable)! Some configure scripts do not recognize --disable-debug. If you see a warning about it, remove the option from the formula.
Homebrew expects to find man pages in [prefix]/share/man/..., and not in [prefix]/man/....
Some software installs to man instead of share/man, so check the output and add a "--mandir=#{man}" to the ./configure line if needed.
THE NAME IS VERY IMPORTANT!
Name the formula like the project markets the product. So it’s pkg-config, not pkgconfig; sdl_mixer, not sdl-mixer or sdlmixer.
The only exception is stuff like “Apache Ant”. Apache sticks “Apache” in front of everything, but we use the formula name ant. We only include the prefix in cases like GNUplot (because it’s part of the name) and GNU Go (because everyone calls it “GNU go”—nobody just calls it “Go”). The word “Go” is too common and there are too many implementations of it.
If you’re not sure about the name check the homepage, and check the Wikipedia page.
ALSO CHECK WHAT DEBIAN CALLS IT!
If you’re still not sure, just commit. I’ll apply some arbitrary rule and make a decision ;)
When importing classes, Homebrew will require the formula and then create an instance of the class. It does this by assuming the formula name can be directly converted to the class name using a regexp. The rules are simple:
| foo-bar.rb | FooBar |
| foobar.rb | Foobar |
Thus, if you change the name of the class, you must also rename the file. Filenames should be all lowercase.
Add aliases by creating symlinks in Library/Aliases.
You can run brew audit to test formulae for adherence to Homebrew house style. This includes warnings for trailing whitespace, preferred URLs for certain source hosts, and a lot of other style issues. Fixing these warnings before committing will make the process a lot smoother for us.
Everything is built on Git, so contribution is easy:
brew install git # if you already have git installed, skip this command
brew update # required in more ways than you think (initializes the brew git repository if you don't already have it)
cd `brew --prefix`
# Create a new git branch for your formula so your pull request is easy to
# modify if any changes come up during review.
git checkout -b <some-descriptive-name>
git add Library/Formula/foo.rb
git commit
The established standard for Git commit messages is:
- the first line is a commit summary of 50 characters or less, then
- two newlines, then
- explain the commit throughly
This may seem crazy short, but you’ll find that forcing yourself to summarise the commit encourages you to be atomic and concise. If you can’t summarise it in 50-80 characters, you’re probably trying to commit two commits as one. For a more thorough explanation, please read Tim Pope’s excellent blog post, A Note About Git Commit Messages.
Ensure you reference any relevant GitHub tickets in the commit message. Homebrew’s history is the first thing future contributors will look to when trying to understand the current state of formulae they’re interested in.
Now you just need to push back to GitHub.
If you haven’t forked Homebrew yet, go to the repo and hit the fork button.
If you have already forked Homebrew on Github, then you can manually push (just make sure you have been pulling from the mxcl/homebrew master):
git push [email protected]:myname/homebrew.git <what-you-called-your-branch>
Now, simply tell a Homebrew collaborator about your formula so it can be merged!
We prefer that you create a Pull Request for new and updated brews.
- One formula per commit; one commit per formula
- Keep merge commits out of the request
- If you have any merge or mixup commits, please squash them.
If a commit touches multiple files, or isn’t one logical bug fix, or a file is touched in multiple commits, we’ll probably ask you to rebase your commits. For this reason, you should create a new remote branch in your fork for each pull request, rather than using your fork’s master branch. You can delete it after we pull your commit.
(Keep Issues for reporting bugs, problems and suggestions.)
- The result of
Formula.download_strategyis instantiated. -
DownloadStrategy.fetchis called (downloads tarball, checks out git repository, etc.) - A temporary sandbox is created in
/tmp/homebrew -
DownloadStrategy.stageis called (extracts tarball to above sandbox, exports git repository to sandbox, etc.) - Patches are applied
- Current directory is changed to the stage root (so when you
system make, it works) -
Formula.installis called - Anything installed to the keg is cleaned (see later)
- The keg is symlinked into Homebrew’s prefix
- Caveats are displayed
Three commands are provided for displaying informational messages to the user:
-
ohaifor general info -
opoofor warning messages -
onoefor error messages
In particular, when a test needs to be performed before installation use onoe to bail out gracefully. For example:
if some_test?
system "make install"
else
onoe 'Error! Something is wrong.'
end
You’ll see stuff like that in other formulae. This installs the file foo into the Formula’s bin directory (`/usr/local/Cellar/pkg/0.1/bin`).
A convenience function that can edit files in-place. For example:
inreplace 'path', before, after
before and after can be strings or regexps. You can also use the block form:
inreplace 'path' do |s|
s.gsub! /foo/, 'bar'
end
Make sure you modify s! This block ignores the returned value.
There are some special functions you can use inside the block that makes it easier to modify Makefiles:
inreplace 'Makefile' do |s|
s.remove_make_var! %w[CFLAGS LDFLAGS CC LD]
s.change_make_var! "CC", ENV.cc
end
NOTE: We really prefer that you use patches. Patches fail to apply if the code changes too much, and this is good! in replace could theoretically continue to apply long after it has subtly broken the code.
While patches should generally be avoided, sometimes they are necessary.
Patches to make the software’s build system respect Homebrew’s installation hierarchy are usually fine and don’t necessitate an upstream bug report, but if the patch is more complex (i.e. fixing header file inclusion, fixing compiler warnings, etc.), the first thing to do is check whether or not the upstream project is aware of the issue. If not, file a bug report and/or submit your patch for inclusion. We will normally still accept your patches, but by getting the ball rolling on fixing the upstream issue, you reduce the length of time we have to carry the patch around.
Always, always, always justify a patch with a comment! Otherwise, nobody will know when it is safe to remove the patch, or safe to leave it in when updating the formula. The comment should include a link to the relevant upstream issue(s).
Return an array or string from your re-implemented patches function:
def patches
# fixes doc install on OS X 10.6
"http://gist.github.com/623/my.patch/raw/"
end
def patches
# fixes multiple problems
[
"http://gist.github.com/623/my-1.patch/raw/",
"http://gist.github.com/623/my-2.patch/raw/",
"http://gist.github.com/623/my-3.patch/raw/"
]
end
Patches can be gzipped…or not. If the patches are not p1, return a Hash:
def patches
# back ported fix for memory leak in drawing functions
{ :p0 => "http://gist.github.com/623/my.patch/raw/" }
end
Small patches should be put in the formula:
class Foo < Formula
def patches
# fixes something small
DATA
end
end
__END__
diff --git a/foo/showfigfonts b/foo/showfigfonts
index 643c60b..543379c 100644
--- a/foo/showfigfonts
+++ b/foo/showfigfonts
@@ -14,6 +14,7 @@
…
The magic variable HOMEBREW_PREFIX is expanded to whatever the Homebrew prefix is before the patch is applied.
We use git for everything…Didn’t you know?
brew install -i --git foo
…
(make some edits)
…
git diff | pbcopy
brew edit foo
Now just paste into the formula after __END__.
If anything isn’t clear, you can usually figure it out with some grep and the Library/Formula directory. Please amend this wiki page if you think it will help!
Formulae can specify alternate downloads for the upstream project’s devel release (unstable but not trunk) or HEAD (master/trunk).
HEAD URLs (activated by passing --HEAD) build the development cutting edge. Specifying it is easy:
class Foo < Formula
head 'https://github.com/mxcl/lastfm-cocoa.git'
end
<code>Homebrew understands git, svn, and hg URLs, and has a way to specify cvs repositories as a URL as well. You can test whether the HEAD is being built with build.head?.
To use a specific commit from a git repository, specify head with the :tag option, like so:
class Foo < Formula
head 'https://github.com/some/package.git', :tag => '090930930295adslfknsdfsdaffnasd13'
end
To use a specific branch from a git repository, specify head with the :branch option, like so:
class Foo < Formula
head 'https://github.com/some/package.git', :branch => 'develop'
end
The ‘devel’ spec (activated by passing --devel) is used for a project’s unstable releases. It is specified in a block:
devel do
url 'https://foo.com/foo-0.1.tar.gz'
sha1 'deadbeefdeadbeefdeadbeafdeadbeefdeadbeef'
end
You can test if the ‘devel’ spec is in use with build.devel?.
Sometimes a package fails to build when using a certain compiler. Since recent Xcode no longer includes a vanilla GCC compiler, we cannot simply force the use of GCC. Instead, the correct way to declare this is the fails_with DSL method. A properly constructed fails_with block documents the latest compiler build version known to cause compilation to fail, and the cause of the failure. For example:
fails_with :llvm do
build 2335
cause <<-EOS.undent
The 'cause' field should include a short summary of the error. Include
the URLs of any relevant information, such as upstream bug reports. Wrap
the text at a sensible boundary (~72-80 characters), but do not break
URLs over multiple lines.
EOS
end
build takes a Fixnum (you can find this number in your brew --config output). cause takes a string, and the use of heredocs is encouraged to improve readability and allow for more comprehensive documentation.
fails_with declarations can be used with any of :gcc, :llvm, and :clang. Homebrew will use this information to select a working compiler (if one is available).
To use one of Homebrew’s built-in download strategies, specify the :using => flag on a url or head. For example:
class Sip < Formula
url 'http://www.riverbankcomputing.co.uk/hg/sip/archive/4.11'
md5 'dbafd7101a4e7caee6f529912a1356e5'
head 'http://www.riverbankcomputing.co.uk/hg/sip', :using => :hg
homepage 'http://www.riverbankcomputing.co.uk/software/sip'
The downloaders offered by Homebrew are:
Value of :using |
Corresponds To |
:bzr |
BazaarDownloadStrategy |
:curl |
CurlDownloadStrategy |
:cvs |
CVSDownloadStrategy |
:git |
GitDownloadStrategy |
:hg |
MercurialDownloadStrategy |
:nounzip |
NoUnzipCurlDownloadStrategy |
:post |
CurlPostDownloadStrategy |
:svn |
SubversionDownloadStrategy |
If you need more control over the way files are downloaded and staged, you can create a custom download strategy and specify it using the Formula#download_strategy function. Return the class type. For example:
class MyDownloadStrategy < SomeHomebrewDownloadStrategy
# Does something cool
end
class Foo < Formula
url "something", :using => MyDownloadStrategy
end
Specifying download strategies can be useful when used with a local repo, where a plain URL would not let you specify how to access it. For example:
class Bar < Formula
head '/users/abc/src/git.git', :using => :git
end
When your code in the install function is run, the current working directory is set to the extracted tarball.
So it is easy to just copy some files:
prefix.install 'file1', 'file2'
Or everything:
prefix.install Dir['*']
| Name | Default | E.g. |
| name | [formula name] | foo |
| HOMEBREW_PREFIX | /usr/local | |
| prefix | #{HOMEBREW_PREFIX}/Cellar/#{name}/#{version} | /usr/local/Cellar/foo/0.1 |
| bin | #{prefix}/bin | /usr/local/Cellar/foo/0.1/bin |
| doc | #{prefix}/share/doc/foo | /usr/local/Cellar/foo/0.1/share/doc/foo |
| include | #{prefix}/include | /usr/local/Cellar/foo/0.1/include |
| info | #{prefix}/share/info | /usr/local/Cellar/foo/0.1/share/info |
| lib | #{prefix}/lib | /usr/local/Cellar/foo/0.1/lib |
| libexec | #{prefix}/libexec | /usr/local/Cellar/foo/0.1/libexec |
| man | #{prefix}/share/man | /usr/local/Cellar/foo/0.1/share/man |
| man[1-8] | #{prefix}/share/man/man[1-8] | /usr/local/Cellar/foo/0.1/share/man/man[1-8] |
| sbin | #{prefix}/sbin | /usr/localCellar/foo/0.1/sbin |
| share | #{prefix}/share | /usr/local/Cellar/foo/0.1/share |
| etc | #{HOMEBREW_PREFIX}/etc | /usr/local/etc |
| var | #{HOMEBREW_PREFIX}/var | /usr/local/var |
These can be used, for instance, in code such as
bin.install Dir['*']
to install binaries into their correct location into the cellar, and
man.mkpath
to create the directory structure to the man location.
To install man pages into specific locations, use man1.install ['foo.1'], man2.install ['foo.2'], etc.
Note that in the context of Homebrew, libexec is reserved for private use by the formula and therefore is not symlinked into HOMEBREW_PREFIX.
If you only need a program for a dependency and it does not need to be linked for public use in /usr/local, specify
keg_only "This is my rationale."
in the formula class.
If you want to add an option:
class Yourformula < Formula
...
option 'option-name', "Description of the option"
option 'another-option', "Another description"
...
And then to define the effects the options have:
if build.include? 'option-name'
...
end
Option names should usually be prefixed with one of the words with, without, no, or a verb in the imperative tense describing the action to be taken. For example, an option to run a test suite should be named --with-test or --with-check rather than --test, and an option to enable a shared library should be named --enable-shared rather than --shared.
See the graphviz formula for an example.
You can use the file utilities provided by Ruby (FileUtils). These are included in the Formula class, so you do not need the FileUtils. prefix to use them.
They are documented here
For example, Ruby 1.9’s gems should be installed to var/lib/ruby/ so that gems don’t need to be reinstalled when upgrading Ruby. You can usually do this with symlink trickery, or better a configure option.
Homebrew provides two Formula methods for launchd plist files. plist_name will return homebrew.mxcl.<formula>, and plist_path will return, for example, /usr/local/Cellar/foo/0.1/homebrew.mxcl.foo.plist.
Homebrew tries to automatically determine the version from the URL in order to save on duplication. If the tarball has a funny name though, you may have to assign the version number:
class Foobar
version "0.7"
end
Homebrew aggressively strips symbols from built binaries. In most cases the only effect of this is smaller resulting binaries, but some times stripping can break executables that use dynamic loading at runtime. In this case, your formula can specify that a given binary should not be stripped; see the Python formula for an example. (When stripped, the python executable fails to load .so based modules.)
Not all projects have makefiles that will run in parallel so try to deparallelize:
brew edit fooAdd all this to the formula (so there will already be a class line, don’t add another or change that, and there’s already an install function, don’t add another one, add the lines in the install function below to the top of the problem formula’s install function).
class Foo < Formula
skip_clean :all
def install
ENV.deparallelize
ENV.no_optimization
system "make" # separate make and make install steps
system "make install"
end
end
If that fixes it, please open an issue so that we can fix it for everyone.
Check out what macports and fink do:
brew -S --macports foo
brew -S --fink foo
superenv is a “super” environment that tries to improve reliability for the general case. But it does make making formula harder.
To not use superenv install with `—env=std`.
Superenv removes /usr/local/bin from the PATH as well as all user-PATHs that are not determined to be essential to the build. It does this because other PATHs are full of stuff that breaks builds. We have 15,000 tickets to that testament.
Superenv tries to remove bad-flags from the commands passed to clang/gcc. But this may break your build as this stuff is not that well-tested yet. If it does, please report it.