68 lines
2.7 KiB
Markdown
68 lines
2.7 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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The [FAQ](FAQ.md#what-does-keg-only-mean) briefly explains this.
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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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This is because Homebrew isolates it within its individual prefix, rather than symlinking to the publicly available location.
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## Advice on potential workarounds
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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* do not remove macOS native tools and forcefully replace them with symlinks back to the Homebrew-provided tool. Doing so can and likely will cause significant breakage when attempting to build software.
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`brew link --force` creates a warning in `brew doctor` to let both you and maintainers know that a link exists that could be causing issues. If you’ve linked something and there’s no problems at all? Feel free to ignore the `brew doctor` error.
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## How do I use those tools outside of Homebrew?
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Useful, reliable alternatives exist should you wish to use keg-only tools outside of Homebrew.
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### Build flags
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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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```sh
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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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```
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An example using `pip`:
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```sh
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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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### `PATH` modification
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You can temporarily prepend your `PATH` with the tool’s `bin` directory, such as:
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```sh
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export PATH="$(brew --prefix)/opt/openssl/bin:${PATH}"
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```
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This will prepend the directory to your `PATH`, ensuring any build script that searches the `PATH` will find it first.
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Changing your `PATH` using this command ensures the change only exists for the duration of the shell session. Once the current session ends, the `PATH` reverts to its prior state.
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### `pkg-config` detection
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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 a keg-only utility’s `.pc` files, if it has any. Not all formulae ship with these files.
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An example of this is:
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```sh
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export PKG_CONFIG_PATH="$(brew --prefix)/opt/openssl/lib/pkgconfig"
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```
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If you’re curious about the `PKG_CONFIG_PATH` variable, `man pkg-config` goes into more detail.
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You can get `pkg-config` to print the default search path with:
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```sh
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pkg-config --variable pc_path pkg-config
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```
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