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How-to-use-keg-only-outside-of-brew: * A new piece of documentation detailing how to deal with using keg_only formula outside of Brew itself. We’ve had a lot of questions and issues about this recently, and the solutions aren’t as easy and explicit to find elsewhere, so detailing it here may help reduce some of the questions we’ve seen recently. * I possibly whinged too much in the second section. I’m open to criticism and being called whiny. * Details flags, prepending the $PATH, and dealing with pkg-config. Closes Homebrew/homebrew#34608. Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
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How to build software outside Homebrew with Homebrew keg-only dependencies.
What does keg-only mean?
See the FAQ on this one. It’s a common question.
As an example:
OpenSSL isn’t symlinked into my $PATH and non-Homebrew builds can’t find it!
That’s because Homebrew keeps it locked away in its prefix, accessible only via its opt directory. keg_only = Not symlinked into the $PATH by default.
But how do I get non-Homebrew builds to find those tools?
A number of people in this situation are either forcefully linking keg_only tools with brew link --force or moving default system utilities out of the $PATH and replacing them with manually-created symlinks to the Homebrew-provided tool.
Please, please do not remove OS X native tools and forcefully replace them with symlinks back to the Homebrew-provided tool. Homebrew doesn’t enforce keg_only onto formulae unless there’s a specific, good reason for doing so, and that reason is usually that forcing that link breaks a whole boat full of builds.
It is also incredibly difficult to debug a build failure if you make changes to the Homebrew-provided tools installed that brew is unaware of. brew link --force deliberately creates a warning in brew doctor to let both you and maintainers know that link exists and could be causing issues.
If you’ve linked something and there’s no problems at all? Awesome, feel free to ignore the brew doctor error. But please don’t try to go around it. It’s really hard to help you out if we don’t know the full picture, and we want to be able to help you if you get stuck.
Alright. Stop complaining at me, I get it - but how do I use those tools outside of Homework?
Useful, reliable alternatives exist should you desire to use keg_only tools outside of Homebrew’s build processes:
You can set flags to give configure scripts or Makefiles a nudge in the right direction. An example of flag setting:
./configure --prefix=/Users/Dave/Downloads CFLAGS=-I$(brew --prefix)/opt/openssl/include LDFLAGS=-L$(brew --prefix)/opt/openssl/lib
An example using pip:
CFLAGS=-I$(brew --prefix)/opt/icu4c/include LDFLAGS=-L$(brew --prefix)/opt/icu4c/lib pip install pyicu
You can temporarily prepend your $PATH with the tool’s bin directory, such as:
export PATH=$(brew --prefix)/opt/openssl/bin:$PATH
This will immediately move that folder to the front of your $PATH, ensuring any build script that searches the $PATH will find it.
Changing your $PATH using that command ensures the change only exists for the duration of that shell session. Once you are no longer in that terminal tab/window, the $PATH ceases to be prepended.
If the tool you are attempting to build is pkg-config aware, you can amend your PKG_CONFIG_PATH to find that keg_only utility’s .pc file, if it has one. Not all formulae ship with those files.
An example of that is:
export PKG_CONFIG_PATH=$(brew --prefix)/opt/openssl/lib/pkgconfig
If you’re curious about PKG_CONFIG_PATH and which paths it searches by default, man pkg-config goes into detail on that.
You can also get pkg-config to detail its currently searched paths with:
pkg-config --variable pc_path pkg-config