54 lines
3.3 KiB
Markdown
54 lines
3.3 KiB
Markdown
# How to build software outside Homebrew with Homebrew keg-only dependencies.
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### What does keg-only mean?
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See the [FAQ](FAQ.md) on this one. It’s a common question.
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As an example:
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*OpenSSL isn’t symlinked into my $PATH and non-Homebrew builds can’t find it!*
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That’s because Homebrew keeps it locked away in its prefix, accessible only via its opt directory. `keg_only` = Not symlinked into the `$PATH` by default.
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### But how do I get non-Homebrew builds to find those tools?
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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 `$PATH` and replacing them with manually-created symlinks to the Homebrew-provided tool.
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Please, *please* do not remove OS X native tools and forcefully replace them with symlinks back to the Homebrew-provided tool. Homebrew doesn’t enforce `keg_only` onto formulae unless there’s a specific, good reason for doing so, and that reason is usually that forcing that link breaks a whole boat full of builds.
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It is also incredibly difficult to debug a build failure if you make changes to the Homebrew-provided tools installed that `brew` is unaware of. `brew link --force` deliberately creates a warning in `brew doctor` to let both you and maintainers know that link exists and could be causing issues.
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If you’ve linked something and there’s no problems at all? Awesome, feel free to ignore the `brew doctor` error. But *please* don’t try to go around it. It’s really hard to help you out if we don’t know the full picture, and we *want* to be able to help you if you get stuck.
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### Alright. Stop complaining at me, I get it - but how do I use those tools outside of Homebrew?
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Useful, reliable alternatives exist should you desire to use `keg_only` tools outside of Homebrew’s build processes:
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----
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You can set flags to give configure scripts or Makefiles a nudge in the right direction. An example of flag setting:
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`./configure --prefix=/Users/Dave/Downloads CFLAGS=-I$(brew --prefix)/opt/openssl/include LDFLAGS=-L$(brew --prefix)/opt/openssl/lib`
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An example using `pip`:
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`CFLAGS=-I$(brew --prefix)/opt/icu4c/include LDFLAGS=-L$(brew --prefix)/opt/icu4c/lib pip install pyicu`
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----
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You can temporarily prepend your `$PATH` with the tool’s bin directory, such as:
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`export PATH=$(brew --prefix)/opt/openssl/bin:$PATH`
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This will immediately move that folder to the front of your `$PATH`, ensuring any build script that searches the `$PATH` will find it.
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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.
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----
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If the tool you are attempting to build is [pkg-config](https://en.wikipedia.org/wiki/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.
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An example of that is:
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`export PKG_CONFIG_PATH=$(brew --prefix)/opt/openssl/lib/pkgconfig `
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If you’re curious about `PKG_CONFIG_PATH` and which paths it searches by default, `man pkg-config` goes into detail on that.
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You can also get `pkg-config` to detail its currently searched paths with:
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`pkg-config --variable pc_path pkg-config`
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