Understanding the relationship between homegrown and keg-only

Question

I recently started using homebrew, and I'm a little confused about what happens when I brew something on my system, but its brewed dependencies are only keg, which means they are bundled in /usr/local .

For example, I install vips (image processing library). One of his many dependencies is pixman. Pixman installs as a keg just because it appears that Mac OSX (Snow Leopard in this case) already comes with it (or its version).

Does this mean that vips will use the pixman system version? If so, are there potential version problems associated with using the system version, not the dependency version (assuming they are different)?

Answer 1

For the software to be "keg-only", it is installed in / usr / local / Cellar, but is not associated with places like / usr / local / bin, / usr / local / lib, etc. This means that other software that depends on it must be compiled with specific instructions for using the files in / usr / local / Cellar. This is done automatically with brew install when the formula defines dependencies for the keg only.

Formulas that define dependencies only on the keg should not contain equivalent system libraries. Your vips installation is associated with a specific pixman version in / usr / local / Cellar / pixman / version, so it is not affected by the pixman system version or any other pixman versions you can install. >