/etc/portage/package.use

 per-package control of USE flags than the USE variable in ]].

The file or directory will override settings coming from the selected profile and the USE variable in.

Example
For more details see the Handbook.

Format

 * One DEPEND atom per line with space-delimited USE flags (see version specifier for information on DEPEND atom syntax).
 * Comment lines begin with  (hash).

Automatically generated content
has the  option enabled by default (see ), so it can generate  settings as necessary to satisfy dependencies.

External resources

 * https://packages.gentoo.org/useflags/ - USE flags on Gentoo Packages Database
 * Portage man page
 * Setting USE_EXPAND flags in package.use - blog post by Bernard Cafarelli
 * Cleaning /etc/portage/package.* from unused entries
 * Find obsolete USE flags in /etc/portage/package.use - Gentoo forums thread