I download the gcc, use brew install gcc but it said the gcc did not linked. how to link the gcc? or what should I do?
When you install gcc with :
brew install gcc
it should be automatically linked. But, if for some reasons, it's not. You can link it manually with :
brew link gcc
The command :
brew link --help
gives also some valuable information :
brew ln, link [--overwrite] [--dry-run] [--force] formula: Symlink all of formula's installed files into the Homebrew prefix. This is done automatically when you install formulae but can be useful for DIY installations. If --overwrite is passed, Homebrew will delete files which already exist in the prefix while linking. If --dry-run or -n is passed, Homebrew will list all files which would be linked or which would be deleted by brew link --overwrite, but will not actually link or delete any files. If --force (or -f) is passed, Homebrew will allow keg-only formulae to be linked.