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keg_only external builds documentation: cleanup

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share/doc/homebrew/How-to-build-software-outside-Homebrew-with-Homebrew-keg-only-dependencies.md
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# How to build software outside Homebrew with Homebrew keg-only dependencies.
# How to build software outside Homebrew with Homebrew `keg-only` dependencies
### What does keg-only mean?
## What does `keg-only` mean?
See the [FAQ](FAQ.md) on this one. It’s a common question.
The [FAQ](FAQ.md) briefly explains this.
As an example:
*OpenSSL isn’t symlinked into my $PATH and non-Homebrew builds can’t find it!*
*OpenSSL isn’t symlinked into my `$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 `$PATH` by default.
This is because Homebrew keeps it locked inside its individual prefix, rather than symlinking to the publicly-available location, usually `/usr/local`.
### How do I get non-Homebrew builds to find those tools?
## Advice on potential workarounds.
A number of people in this situation are either forcefully linking `keg_only` tools with `brew link --force` or moving default system utilities out of the `$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.
*Please* do not remove OS X 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.
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.
`brew link --force` 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? Feel free to ignore the `brew doctor` error.
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.
## How do I use those tools outside of Homebrew?
### How do I use those tools outside of Homebrew?
Useful, reliable alternatives exist should you wish to use `keg_only` tools outside of Homebrew.
### Build flags:
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:
```shell
@ -37,7 +37,7 @@ An example using `pip`:
CFLAGS=-I$(brew --prefix)/opt/icu4c/include LDFLAGS=-L$(brew --prefix)/opt/icu4c/lib pip install pyicu
```
----
### `$PATH` modification:
You can temporarily prepend your `$PATH` with the tool’s bin directory, such as:
@ -45,13 +45,13 @@ You can temporarily prepend your `$PATH` with the tool’s bin directory, such a
export PATH=$(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 `$PATH` will find it.
This will prepend that folder to your `$PATH`, ensuring any build script that searches the `$PATH` will find it first.
Changing your `$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 `$PATH` ceases to be prepended.
Changing your `$PATH` using that command ensures the change only exists for the duration of that shell session. Once you are no longer in that session, the `$PATH` reverts to the prior state.
----
### `pkg-config` detection:
If the tool you are attempting to build is [pkg-config](https://en.wikipedia.org/wiki/Pkg-config) aware, you can amend your `PKG_CONFIG_PATH` to find that `keg_only` utility’s `.pc` file, if it has one. Not all formulae ship with those files.
If the tool you are attempting to build is [pkg-config](https://en.wikipedia.org/wiki/Pkg-config) aware, you can amend your `PKG_CONFIG_PATH` to find that `keg_only` utility’s `.pc` file, if it has them. Not all formulae ship with those files.
An example of that is:
@ -59,10 +59,10 @@ An example of that is:
export PKG_CONFIG_PATH=$(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.
If you’re curious about the `PKG_CONFIG_PATH` variable `man pkg-config` goes into more detail.
You can also get `pkg-config` to detail its currently searched paths with:
You can get `pkg-config` to detail the default search path with:
```shell
pkg-config --variable pc_path pkg-config`
pkg-config --variable pc_path pkg-config
```