Excerpt from homebrew's formula_installer.rb

formula_installer-excerpt.rb

  def link
    if f.linked_keg.directory? and f.linked_keg.realpath == f.prefix
      opoo "This keg was marked linked already, continuing anyway"
      # otherwise Keg.link will bail
      f.linked_keg.unlink
    end

    keg = Keg.new(f.prefix)
    keg.link
  rescue Exception => e
    onoe "The linking step did not complete successfully"
    puts "The formula built, but is not symlinked into #{HOMEBREW_PREFIX}"
    puts "You can try again using `brew link #{f.name}'"
    keg.unlink

    ohai e, e.backtrace if ARGV.debug?
    @show_summary_heading = true
  end

  def fix_install_names
    Keg.new(f.prefix).fix_install_names
  rescue Exception => e
    onoe "Failed to fix install names"
    puts "The formula built, but you may encounter issues using it or linking other"
    puts "formula against it."
    ohai e, e.backtrace if ARGV.debug?
    @show_summary_heading = true
  end

  def clean
    require 'cleaner'
    Cleaner.new f
  rescue Exception => e
    opoo "The cleaning step did not complete successfully"
    puts "Still, the installation was successful, so we will link it into your prefix"
    ohai e, e.backtrace if ARGV.debug?
    @show_summary_heading = true
  end

  def pour
    fetched, downloader = f.fetch
    f.verify_download_integrity fetched, f.bottle_sha1, "SHA1"
    HOMEBREW_CELLAR.cd do
      downloader.stage
    end
  end