ruby/lib/fileutils.rb

# frozen_string_literal: true

begin
  require 'rbconfig'
rescue LoadError
  # for make mjit-headers
end

require "fileutils/version"

#
# = fileutils.rb
#
# Copyright (c) 2000-2007 Minero Aoki
#
# This program is free software.
# You can distribute/modify this program under the same terms of ruby.
#
# == module FileUtils
#
# Namespace for several file utility methods for copying, moving, removing, etc.
#
# === Module Functions
#
#   require 'fileutils'
#
#   FileUtils.cd(dir, options)
#   FileUtils.cd(dir, options) {|dir| block }
#   FileUtils.pwd()
#   FileUtils.mkdir(dir, options)
#   FileUtils.mkdir(list, options)
#   FileUtils.mkdir_p(dir, options)
#   FileUtils.mkdir_p(list, options)
#   FileUtils.rmdir(dir, options)
#   FileUtils.rmdir(list, options)
#   FileUtils.ln(target, link, options)
#   FileUtils.ln(targets, dir, options)
#   FileUtils.ln_s(target, link, options)
#   FileUtils.ln_s(targets, dir, options)
#   FileUtils.ln_sf(target, link, options)
#   FileUtils.cp(src, dest, options)
#   FileUtils.cp(list, dir, options)
#   FileUtils.cp_r(src, dest, options)
#   FileUtils.cp_r(list, dir, options)
#   FileUtils.mv(src, dest, options)
#   FileUtils.mv(list, dir, options)
#   FileUtils.rm(list, options)
#   FileUtils.rm_r(list, options)
#   FileUtils.rm_rf(list, options)
#   FileUtils.install(src, dest, options)
#   FileUtils.chmod(mode, list, options)
#   FileUtils.chmod_R(mode, list, options)
#   FileUtils.chown(user, group, list, options)
#   FileUtils.chown_R(user, group, list, options)
#   FileUtils.touch(list, options)
#
# The <tt>options</tt> parameter is a hash of options, taken from the list
# <tt>:force</tt>, <tt>:noop</tt>, <tt>:preserve</tt>, and <tt>:verbose</tt>.
# <tt>:noop</tt> means that no changes are made.  The other three are obvious.
# Each method documents the options that it honours.
#
# All methods that have the concept of a "source" file or directory can take
# either one file or a list of files in that argument.  See the method
# documentation for examples.
#
# There are some `low level' methods, which do not accept any option:
#
#   FileUtils.copy_entry(src, dest, preserve = false, dereference_root = false, remove_destination = false)
#   FileUtils.copy_file(src, dest, preserve = false, dereference = true)
#   FileUtils.copy_stream(srcstream, deststream)
#   FileUtils.remove_entry(path, force = false)
#   FileUtils.remove_entry_secure(path, force = false)
#   FileUtils.remove_file(path, force = false)
#   FileUtils.compare_file(path_a, path_b)
#   FileUtils.compare_stream(stream_a, stream_b)
#   FileUtils.uptodate?(file, cmp_list)
#
# == module FileUtils::Verbose
#
# This module has all methods of FileUtils module, but it outputs messages
# before acting.  This equates to passing the <tt>:verbose</tt> flag to methods
# in FileUtils.
#
# == module FileUtils::NoWrite
#
# This module has all methods of FileUtils module, but never changes
# files/directories.  This equates to passing the <tt>:noop</tt> flag to methods
# in FileUtils.
#
# == module FileUtils::DryRun
#
# This module has all methods of FileUtils module, but never changes
# files/directories.  This equates to passing the <tt>:noop</tt> and
# <tt>:verbose</tt> flags to methods in FileUtils.
#
module FileUtils

  def self.private_module_function(name)   #:nodoc:
    module_function name
    private_class_method name
  end

  #
  # Returns the name of the current directory.
  #
  def pwd
    Dir.pwd
  end
  module_function :pwd

  alias getwd pwd
  module_function :getwd

  #
  # Changes the current directory to the directory +dir+.
  #
  # If this method is called with block, resumes to the old
  # working directory after the block execution finished.
  #
  #   FileUtils.cd('/', :verbose => true)   # chdir and report it
  #
  #   FileUtils.cd('/') do  # chdir
  #     # ...               # do something
  #   end                   # return to original directory
  #
  def cd(dir, verbose: nil, &block) # :yield: dir
    fu_output_message "cd #{dir}" if verbose
    result = Dir.chdir(dir, &block)
    fu_output_message 'cd -' if verbose and block
    result
  end
  module_function :cd

  alias chdir cd
  module_function :chdir

  #
  # Returns true if +new+ is newer than all +old_list+.
  # Non-existent files are older than any file.
  #
  #   FileUtils.uptodate?('hello.o', %w(hello.c hello.h)) or \
  #       system 'make hello.o'
  #
  def uptodate?(new, old_list)
    return false unless File.exist?(new)
    new_time = File.mtime(new)
    old_list.each do |old|
      if File.exist?(old)
        return false unless new_time > File.mtime(old)
      end
    end
    true
  end
  module_function :uptodate?

  def remove_trailing_slash(dir)   #:nodoc:
    dir == '/' ? dir : dir.chomp(?/)
  end
  private_module_function :remove_trailing_slash

  #
  # Creates one or more directories.
  #
  #   FileUtils.mkdir 'test'
  #   FileUtils.mkdir %w( tmp data )
  #   FileUtils.mkdir 'notexist', :noop => true  # Does not really create.
  #   FileUtils.mkdir 'tmp', :mode => 0700
  #
  def mkdir(list, mode: nil, noop: nil, verbose: nil)
    list = fu_list(list)
    fu_output_message "mkdir #{mode ? ('-m %03o ' % mode) : ''}#{list.join ' '}" if verbose
    return if noop

    list.each do |dir|
      fu_mkdir dir, mode
    end
  end
  module_function :mkdir

  #
  # Creates a directory and all its parent directories.
  # For example,
  #
  #   FileUtils.mkdir_p '/usr/local/lib/ruby'
  #
  # causes to make following directories, if it does not exist.
  #
  # * /usr
  # * /usr/local
  # * /usr/local/lib
  # * /usr/local/lib/ruby
  #
  # You can pass several directories at a time in a list.
  #
  def mkdir_p(list, mode: nil, noop: nil, verbose: nil)
    list = fu_list(list)
    fu_output_message "mkdir -p #{mode ? ('-m %03o ' % mode) : ''}#{list.join ' '}" if verbose
    return *list if noop

    list.map {|path| remove_trailing_slash(path)}.each do |path|
      # optimize for the most common case
      begin
        fu_mkdir path, mode
        next
      rescue SystemCallError
        next if File.directory?(path)
      end

      stack = []
      until path == stack.last   # dirname("/")=="/", dirname("C:/")=="C:/"
        stack.push path
        path = File.dirname(path)
      end
      stack.pop                 # root directory should exist
      stack.reverse_each do |dir|
        begin
          fu_mkdir dir, mode
        rescue SystemCallError
          raise unless File.directory?(dir)
        end
      end
    end

    return *list
  end
  module_function :mkdir_p

  alias mkpath    mkdir_p
  alias makedirs  mkdir_p
  module_function :mkpath
  module_function :makedirs

  def fu_mkdir(path, mode)   #:nodoc:
    path = remove_trailing_slash(path)
    if mode
      Dir.mkdir path, mode
      File.chmod mode, path
    else
      Dir.mkdir path
    end
  end
  private_module_function :fu_mkdir

  #
  # Removes one or more directories.
  #
  #   FileUtils.rmdir 'somedir'
  #   FileUtils.rmdir %w(somedir anydir otherdir)
  #   # Does not really remove directory; outputs message.
  #   FileUtils.rmdir 'somedir', :verbose => true, :noop => true
  #
  def rmdir(list, parents: nil, noop: nil, verbose: nil)
    list = fu_list(list)
    fu_output_message "rmdir #{parents ? '-p ' : ''}#{list.join ' '}" if verbose
    return if noop
    list.each do |dir|
      Dir.rmdir(dir = remove_trailing_slash(dir))
      if parents
        begin
          until (parent = File.dirname(dir)) == '.' or parent == dir
            dir = parent
            Dir.rmdir(dir)
          end
        rescue Errno::ENOTEMPTY, Errno::EEXIST, Errno::ENOENT
        end
      end
    end
  end
  module_function :rmdir

  #
  # :call-seq:
  #   FileUtils.ln(target, link, force: nil, noop: nil, verbose: nil)
  #   FileUtils.ln(target,  dir, force: nil, noop: nil, verbose: nil)
  #   FileUtils.ln(targets, dir, force: nil, noop: nil, verbose: nil)
  #
  # In the first form, creates a hard link +link+ which points to +target+.
  # If +link+ already exists, raises Errno::EEXIST.
  # But if the :force option is set, overwrites +link+.
  #
  #   FileUtils.ln 'gcc', 'cc', verbose: true
  #   FileUtils.ln '/usr/bin/emacs21', '/usr/bin/emacs'
  #
  # In the second form, creates a link +dir/target+ pointing to +target+.
  # In the third form, creates several hard links in the directory +dir+,
  # pointing to each item in +targets+.
  # If +dir+ is not a directory, raises Errno::ENOTDIR.
  #
  #   FileUtils.cd '/sbin'
  #   FileUtils.ln %w(cp mv mkdir), '/bin'   # Now /sbin/cp and /bin/cp are linked.
  #
  def ln(src, dest, force: nil, noop: nil, verbose: nil)
    fu_output_message "ln#{force ? ' -f' : ''} #{[src,dest].flatten.join ' '}" if verbose
    return if noop
    fu_each_src_dest0(src, dest) do |s,d|
      remove_file d, true if force
      File.link s, d
    end
  end
  module_function :ln

  alias link ln
  module_function :link

  #
  # :call-seq:
  #   FileUtils.cp_lr(src, dest, noop: nil, verbose: nil, dereference_root: true, remove_destination: false)
  #
  # Hard link +src+ to +dest+. If +src+ is a directory, this method links
  # all its contents recursively. If +dest+ is a directory, links
  # +src+ to +dest/src+.
  #
  # +src+ can be a list of files.
  #
  #   # Installing the library "mylib" under the site_ruby directory.
  #   FileUtils.rm_r site_ruby + '/mylib', :force => true
  #   FileUtils.cp_lr 'lib/', site_ruby + '/mylib'
  #
  #   # Examples of linking several files to target directory.
  #   FileUtils.cp_lr %w(mail.rb field.rb debug/), site_ruby + '/tmail'
  #   FileUtils.cp_lr Dir.glob('*.rb'), '/home/aamine/lib/ruby', :noop => true, :verbose => true
  #
  #   # If you want to link all contents of a directory instead of the
  #   # directory itself, c.f. src/x -> dest/x, src/y -> dest/y,
  #   # use the following code.
  #   FileUtils.cp_lr 'src/.', 'dest'  # cp_lr('src', 'dest') makes dest/src, but this doesn't.
  #
  def cp_lr(src, dest, noop: nil, verbose: nil,
            dereference_root: true, remove_destination: false)
    fu_output_message "cp -lr#{remove_destination ? ' --remove-destination' : ''} #{[src,dest].flatten.join ' '}" if verbose
    return if noop
    fu_each_src_dest(src, dest) do |s, d|
      link_entry s, d, dereference_root, remove_destination
    end
  end
  module_function :cp_lr

  #
  # :call-seq:
  #   FileUtils.ln_s(target, link, force: nil, noop: nil, verbose: nil)
  #   FileUtils.ln_s(target,  dir, force: nil, noop: nil, verbose: nil)
  #   FileUtils.ln_s(targets, dir, force: nil, noop: nil, verbose: nil)
  #
  # In the first form, creates a symbolic link +link+ which points to +target+.
  # If +link+ already exists, raises Errno::EEXIST.
  # But if the :force option is set, overwrites +link+.
  #
  #   FileUtils.ln_s '/usr/bin/ruby', '/usr/local/bin/ruby'
  #   FileUtils.ln_s 'verylongsourcefilename.c', 'c', force: true
  #
  # In the second form, creates a link +dir/target+ pointing to +target+.
  # In the third form, creates several symbolic links in the directory +dir+,
  # pointing to each item in +targets+.
  # If +dir+ is not a directory, raises Errno::ENOTDIR.
  #
  #   FileUtils.ln_s Dir.glob('/bin/*.rb'), '/home/foo/bin'
  #
  def ln_s(src, dest, force: nil, noop: nil, verbose: nil)
    fu_output_message "ln -s#{force ? 'f' : ''} #{[src,dest].flatten.join ' '}" if verbose
    return if noop
    fu_each_src_dest0(src, dest) do |s,d|
      remove_file d, true if force
      File.symlink s, d
    end
  end
  module_function :ln_s

  alias symlink ln_s
  module_function :symlink

  #
  # :call-seq:
  #   FileUtils.ln_sf(*args)
  #
  # Same as
  #
  #   FileUtils.ln_s(*args, force: true)
  #
  def ln_sf(src, dest, noop: nil, verbose: nil)
    ln_s src, dest, force: true, noop: noop, verbose: verbose
  end
  module_function :ln_sf

  #
  # Hard links a file system entry +src+ to +dest+.
  # If +src+ is a directory, this method links its contents recursively.
  #
  # Both of +src+ and +dest+ must be a path name.
  # +src+ must exist, +dest+ must not exist.
  #
  # If +dereference_root+ is true, this method dereferences the tree root.
  #
  # If +remove_destination+ is true, this method removes each destination file before copy.
  #
  def link_entry(src, dest, dereference_root = false, remove_destination = false)
    Entry_.new(src, nil, dereference_root).traverse do |ent|
      destent = Entry_.new(dest, ent.rel, false)
      File.unlink destent.path if remove_destination && File.file?(destent.path)
      ent.link destent.path
    end
  end
  module_function :link_entry

  #
  # Copies a file content +src+ to +dest+.  If +dest+ is a directory,
  # copies +src+ to +dest/src+.
  #
  # If +src+ is a list of files, then +dest+ must be a directory.
  #
  #   FileUtils.cp 'eval.c', 'eval.c.org'
  #   FileUtils.cp %w(cgi.rb complex.rb date.rb), '/usr/lib/ruby/1.6'
  #   FileUtils.cp %w(cgi.rb complex.rb date.rb), '/usr/lib/ruby/1.6', :verbose => true
  #   FileUtils.cp 'symlink', 'dest'   # copy content, "dest" is not a symlink
  #
  def cp(src, dest, preserve: nil, noop: nil, verbose: nil)
    fu_output_message "cp#{preserve ? ' -p' : ''} #{[src,dest].flatten.join ' '}" if verbose
    return if noop
    fu_each_src_dest(src, dest) do |s, d|
      copy_file s, d, preserve
    end
  end
  module_function :cp

  alias copy cp
  module_function :copy

  #
  # Copies +src+ to +dest+. If +src+ is a directory, this method copies
  # all its contents recursively. If +dest+ is a directory, copies
  # +src+ to +dest/src+.
  #
  # +src+ can be a list of files.
  #
  #   # Installing Ruby library "mylib" under the site_ruby
  #   FileUtils.rm_r site_ruby + '/mylib', :force
  #   FileUtils.cp_r 'lib/', site_ruby + '/mylib'
  #
  #   # Examples of copying several files to target directory.
  #   FileUtils.cp_r %w(mail.rb field.rb debug/), site_ruby + '/tmail'
  #   FileUtils.cp_r Dir.glob('*.rb'), '/home/foo/lib/ruby', :noop => true, :verbose => true
  #
  #   # If you want to copy all contents of a directory instead of the
  #   # directory itself, c.f. src/x -> dest/x, src/y -> dest/y,
  #   # use following code.
  #   FileUtils.cp_r 'src/.', 'dest'     # cp_r('src', 'dest') makes dest/src,
  #                                      # but this doesn't.
  #
  def cp_r(src, dest, preserve: nil, noop: nil, verbose: nil,
           dereference_root: true, remove_destination: nil)
    fu_output_message "cp -r#{preserve ? 'p' : ''}#{remove_destination ? ' --remove-destination' : ''} #{[src,dest].flatten.join ' '}" if verbose
    return if noop
    fu_each_src_dest(src, dest) do |s, d|
      copy_entry s, d, preserve, dereference_root, remove_destination
    end
  end
  module_function :cp_r

  #
  # Copies a file system entry +src+ to +dest+.
  # If +src+ is a directory, this method copies its contents recursively.
  # This method preserves file types, c.f. symlink, directory...
  # (FIFO, device files and etc. are not supported yet)
  #
  # Both of +src+ and +dest+ must be a path name.
  # +src+ must exist, +dest+ must not exist.
  #
  # If +preserve+ is true, this method preserves owner, group, and
  # modified time.  Permissions are copied regardless +preserve+.
  #
  # If +dereference_root+ is true, this method dereference tree root.
  #
  # If +remove_destination+ is true, this method removes each destination file before copy.
  #
  def copy_entry(src, dest, preserve = false, dereference_root = false, remove_destination = false)
    Entry_.new(src, nil, dereference_root).wrap_traverse(proc do |ent|
      destent = Entry_.new(dest, ent.rel, false)
      File.unlink destent.path if remove_destination && (File.file?(destent.path) || File.symlink?(destent.path))
      ent.copy destent.path
    end, proc do |ent|
      destent = Entry_.new(dest, ent.rel, false)
      ent.copy_metadata destent.path if preserve
    end)
  end
  module_function :copy_entry

  #
  # Copies file contents of +src+ to +dest+.
  # Both of +src+ and +dest+ must be a path name.
  #
  def copy_file(src, dest, preserve = false, dereference = true)
    ent = Entry_.new(src, nil, dereference)
    ent.copy_file dest
    ent.copy_metadata dest if preserve
  end
  module_function :copy_file

  #
  # Copies stream +src+ to +dest+.
  # +src+ must respond to #read(n) and
  # +dest+ must respond to #write(str).
  #
  def copy_stream(src, dest)
    IO.copy_stream(src, dest)
  end
  module_function :copy_stream

  #
  # Moves file(s) +src+ to +dest+.  If +file+ and +dest+ exist on the different
  # disk partition, the file is copied then the original file is removed.
  #
  #   FileUtils.mv 'badname.rb', 'goodname.rb'
  #   FileUtils.mv 'stuff.rb', '/notexist/lib/ruby', :force => true  # no error
  #
  #   FileUtils.mv %w(junk.txt dust.txt), '/home/foo/.trash/'
  #   FileUtils.mv Dir.glob('test*.rb'), 'test', :noop => true, :verbose => true
  #
  def mv(src, dest, force: nil, noop: nil, verbose: nil, secure: nil)
    fu_output_message "mv#{force ? ' -f' : ''} #{[src,dest].flatten.join ' '}" if verbose
    return if noop
    fu_each_src_dest(src, dest) do |s, d|
      destent = Entry_.new(d, nil, true)
      begin
        if destent.exist?
          if destent.directory?
            raise Errno::EEXIST, d
          end
        end
        begin
          File.rename s, d
        rescue Errno::EXDEV
          copy_entry s, d, true
          if secure
            remove_entry_secure s, force
          else
            remove_entry s, force
          end
        end
      rescue SystemCallError
        raise unless force
      end
    end
  end
  module_function :mv

  alias move mv
  module_function :move

  #
  # Remove file(s) specified in +list+.  This method cannot remove directories.
  # All StandardErrors are ignored when the :force option is set.
  #
  #   FileUtils.rm %w( junk.txt dust.txt )
  #   FileUtils.rm Dir.glob('*.so')
  #   FileUtils.rm 'NotExistFile', :force => true   # never raises exception
  #
  def rm(list, force: nil, noop: nil, verbose: nil)
    list = fu_list(list)
    fu_output_message "rm#{force ? ' -f' : ''} #{list.join ' '}" if verbose
    return if noop

    list.each do |path|
      remove_file path, force
    end
  end
  module_function :rm

  alias remove rm
  module_function :remove

  #
  # Equivalent to
  #
  #   FileUtils.rm(list, :force => true)
  #
  def rm_f(list, noop: nil, verbose: nil)
    rm list, force: true, noop: noop, verbose: verbose
  end
  module_function :rm_f

  alias safe_unlink rm_f
  module_function :safe_unlink

  #
  # remove files +list+[0] +list+[1]... If +list+[n] is a directory,
  # removes its all contents recursively. This method ignores
  # StandardError when :force option is set.
  #
  #   FileUtils.rm_r Dir.glob('/tmp/*')
  #   FileUtils.rm_r 'some_dir', :force => true
  #
  # WARNING: This method causes local vulnerability
  # if one of parent directories or removing directory tree are world
  # writable (including /tmp, whose permission is 1777), and the current
  # process has strong privilege such as Unix super user (root), and the
  # system has symbolic link.  For secure removing, read the documentation
  # of #remove_entry_secure carefully, and set :secure option to true.
  # Default is :secure=>false.
  #
  # NOTE: This method calls #remove_entry_secure if :secure option is set.
  # See also #remove_entry_secure.
  #
  def rm_r(list, force: nil, noop: nil, verbose: nil, secure: nil)
    list = fu_list(list)
    fu_output_message "rm -r#{force ? 'f' : ''} #{list.join ' '}" if verbose
    return if noop
    list.each do |path|
      if secure
        remove_entry_secure path, force
      else
        remove_entry path, force
      end
    end
  end
  module_function :rm_r

  #
  # Equivalent to
  #
  #   FileUtils.rm_r(list, :force => true)
  #
  # WARNING: This method causes local vulnerability.
  # Read the documentation of #rm_r first.
  #
  def rm_rf(list, noop: nil, verbose: nil, secure: nil)
    rm_r list, force: true, noop: noop, verbose: verbose, secure: secure
  end
  module_function :rm_rf

  alias rmtree rm_rf
  module_function :rmtree

  #
  # This method removes a file system entry +path+.  +path+ shall be a
  # regular file, a directory, or something.  If +path+ is a directory,
  # remove it recursively.  This method is required to avoid TOCTTOU
  # (time-of-check-to-time-of-use) local security vulnerability of #rm_r.
  # #rm_r causes security hole when:
  #
  # * Parent directory is world writable (including /tmp).
  # * Removing directory tree includes world writable directory.
  # * The system has symbolic link.
  #
  # To avoid this security hole, this method applies special preprocess.
  # If +path+ is a directory, this method chown(2) and chmod(2) all
  # removing directories.  This requires the current process is the
  # owner of the removing whole directory tree, or is the super user (root).
  #
  # WARNING: You must ensure that *ALL* parent directories cannot be
  # moved by other untrusted users.  For example, parent directories
  # should not be owned by untrusted users, and should not be world
  # writable except when the sticky bit set.
  #
  # WARNING: Only the owner of the removing directory tree, or Unix super
  # user (root) should invoke this method.  Otherwise this method does not
  # work.
  #
  # For details of this security vulnerability, see Perl's case:
  #
  # * https://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-0448
  # * https://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0452
  #
  # For fileutils.rb, this vulnerability is reported in [ruby-dev:26100].
  #
  def remove_entry_secure(path, force = false)
    unless fu_have_symlink?
      remove_entry path, force
      return
    end
    fullpath = File.expand_path(path)
    st = File.lstat(fullpath)
    unless st.directory?
      File.unlink fullpath
      return
    end
    # is a directory.
    parent_st = File.stat(File.dirname(fullpath))
    unless parent_st.world_writable?
      remove_entry path, force
      return
    end
    unless parent_st.sticky?
      raise ArgumentError, "parent directory is world writable, FileUtils#remove_entry_secure does not work; abort: #{path.inspect} (parent directory mode #{'%o' % parent_st.mode})"
    end

    # freeze tree root
    euid = Process.euid
    dot_file = fullpath + "/."
    begin
      File.open(dot_file) {|f|
        unless fu_stat_identical_entry?(st, f.stat)
          # symlink (TOC-to-TOU attack?)
          File.unlink fullpath
          return
        end
        f.chown euid, -1
        f.chmod 0700
      }
    rescue EISDIR # JRuby in non-native mode can't open files as dirs
      File.lstat(dot_file).tap {|fstat|
        unless fu_stat_identical_entry?(st, fstat)
          # symlink (TOC-to-TOU attack?)
          File.unlink fullpath
          return
        end
        File.chown euid, -1, dot_file
        File.chmod 0700, dot_file
      }
    end

    unless fu_stat_identical_entry?(st, File.lstat(fullpath))
      # TOC-to-TOU attack?
      File.unlink fullpath
      return
    end

    # ---- tree root is frozen ----
    root = Entry_.new(path)
    root.preorder_traverse do |ent|
      if ent.directory?
        ent.chown euid, -1
        ent.chmod 0700
      end
    end
    root.postorder_traverse do |ent|
      begin
        ent.remove
      rescue
        raise unless force
      end
    end
  rescue
    raise unless force
  end
  module_function :remove_entry_secure

  def fu_have_symlink?   #:nodoc:
    File.symlink nil, nil
  rescue NotImplementedError
    return false
  rescue TypeError
    return true
  end
  private_module_function :fu_have_symlink?

  def fu_stat_identical_entry?(a, b)   #:nodoc:
    a.dev == b.dev and a.ino == b.ino
  end
  private_module_function :fu_stat_identical_entry?

  #
  # This method removes a file system entry +path+.
  # +path+ might be a regular file, a directory, or something.
  # If +path+ is a directory, remove it recursively.
  #
  # See also #remove_entry_secure.
  #
  def remove_entry(path, force = false)
    Entry_.new(path).postorder_traverse do |ent|
      begin
        ent.remove
      rescue
        raise unless force
      end
    end
  rescue
    raise unless force
  end
  module_function :remove_entry

  #
  # Removes a file +path+.
  # This method ignores StandardError if +force+ is true.
  #
  def remove_file(path, force = false)
    Entry_.new(path).remove_file
  rescue
    raise unless force
  end
  module_function :remove_file

  #
  # Removes a directory +dir+ and its contents recursively.
  # This method ignores StandardError if +force+ is true.
  #
  def remove_dir(path, force = false)
    remove_entry path, force   # FIXME?? check if it is a directory
  end
  module_function :remove_dir

  #
  # Returns true if the contents of a file +a+ and a file +b+ are identical.
  #
  #   FileUtils.compare_file('somefile', 'somefile')       #=> true
  #   FileUtils.compare_file('/dev/null', '/dev/urandom')  #=> false
  #
  def compare_file(a, b)
    return false unless File.size(a) == File.size(b)
    File.open(a, 'rb') {|fa|
      File.open(b, 'rb') {|fb|
        return compare_stream(fa, fb)
      }
    }
  end
  module_function :compare_file

  alias identical? compare_file
  alias cmp compare_file
  module_function :identical?
  module_function :cmp

  #
  # Returns true if the contents of a stream +a+ and +b+ are identical.
  #
  def compare_stream(a, b)
    bsize = fu_stream_blksize(a, b)

    if RUBY_VERSION > "2.4"
      sa = String.new(capacity: bsize)
      sb = String.new(capacity: bsize)
    else
      sa = String.new
      sb = String.new
    end

    begin
      a.read(bsize, sa)
      b.read(bsize, sb)
      return true if sa.empty? && sb.empty?
    end while sa == sb
    false
  end
  module_function :compare_stream

  #
  # If +src+ is not same as +dest+, copies it and changes the permission
  # mode to +mode+.  If +dest+ is a directory, destination is +dest+/+src+.
  # This method removes destination before copy.
  #
  #   FileUtils.install 'ruby', '/usr/local/bin/ruby', :mode => 0755, :verbose => true
  #   FileUtils.install 'lib.rb', '/usr/local/lib/ruby/site_ruby', :verbose => true
  #
  def install(src, dest, mode: nil, owner: nil, group: nil, preserve: nil,
              noop: nil, verbose: nil)
    if verbose
      msg = +"install -c"
      msg << ' -p' if preserve
      msg << ' -m ' << mode_to_s(mode) if mode
      msg << " -o #{owner}" if owner
      msg << " -g #{group}" if group
      msg << ' ' << [src,dest].flatten.join(' ')
      fu_output_message msg
    end
    return if noop
    uid = fu_get_uid(owner)
    gid = fu_get_gid(group)
    fu_each_src_dest(src, dest) do |s, d|
      st = File.stat(s)
      unless File.exist?(d) and compare_file(s, d)
        remove_file d, true
        copy_file s, d
        File.utime st.atime, st.mtime, d if preserve
        File.chmod fu_mode(mode, st), d if mode
        File.chown uid, gid, d if uid or gid
      end
    end
  end
  module_function :install

  def user_mask(target)  #:nodoc:
    target.each_char.inject(0) do |mask, chr|
      case chr
      when "u"
        mask | 04700
      when "g"
        mask | 02070
      when "o"
        mask | 01007
      when "a"
        mask | 07777
      else
        raise ArgumentError, "invalid `who' symbol in file mode: #{chr}"
      end
    end
  end
  private_module_function :user_mask

  def apply_mask(mode, user_mask, op, mode_mask)   #:nodoc:
    case op
    when '='
      (mode & ~user_mask) | (user_mask & mode_mask)
    when '+'
      mode | (user_mask & mode_mask)
    when '-'
      mode & ~(user_mask & mode_mask)
    end
  end
  private_module_function :apply_mask

  def symbolic_modes_to_i(mode_sym, path)  #:nodoc:
    mode = if File::Stat === path
             path.mode
           else
             File.stat(path).mode
           end
    mode_sym.split(/,/).inject(mode & 07777) do |current_mode, clause|
      target, *actions = clause.split(/([=+-])/)
      raise ArgumentError, "invalid file mode: #{mode_sym}" if actions.empty?
      target = 'a' if target.empty?
      user_mask = user_mask(target)
      actions.each_slice(2) do |op, perm|
        need_apply = op == '='
        mode_mask = (perm || '').each_char.inject(0) do |mask, chr|
          case chr
          when "r"
            mask | 0444
          when "w"
            mask | 0222
          when "x"
            mask | 0111
          when "X"
            if FileTest.directory? path
              mask | 0111
            else
              mask
            end
          when "s"
            mask | 06000
          when "t"
            mask | 01000
          when "u", "g", "o"
            if mask.nonzero?
              current_mode = apply_mask(current_mode, user_mask, op, mask)
            end
            need_apply = false
            copy_mask = user_mask(chr)
            (current_mode & copy_mask) / (copy_mask & 0111) * (user_mask & 0111)
          else
            raise ArgumentError, "invalid `perm' symbol in file mode: #{chr}"
          end
        end

        if mode_mask.nonzero? || need_apply
          current_mode = apply_mask(current_mode, user_mask, op, mode_mask)
        end
      end
      current_mode
    end
  end
  private_module_function :symbolic_modes_to_i

  def fu_mode(mode, path)  #:nodoc:
    mode.is_a?(String) ? symbolic_modes_to_i(mode, path) : mode
  end
  private_module_function :fu_mode

  def mode_to_s(mode)  #:nodoc:
    mode.is_a?(String) ? mode : "%o" % mode
  end
  private_module_function :mode_to_s

  #
  # Changes permission bits on the named files (in +list+) to the bit pattern
  # represented by +mode+.
  #
  # +mode+ is the symbolic and absolute mode can be used.
  #
  # Absolute mode is
  #   FileUtils.chmod 0755, 'somecommand'
  #   FileUtils.chmod 0644, %w(my.rb your.rb his.rb her.rb)
  #   FileUtils.chmod 0755, '/usr/bin/ruby', :verbose => true
  #
  # Symbolic mode is
  #   FileUtils.chmod "u=wrx,go=rx", 'somecommand'
  #   FileUtils.chmod "u=wr,go=rr", %w(my.rb your.rb his.rb her.rb)
  #   FileUtils.chmod "u=wrx,go=rx", '/usr/bin/ruby', :verbose => true
  #
  # "a" :: is user, group, other mask.
  # "u" :: is user's mask.
  # "g" :: is group's mask.
  # "o" :: is other's mask.
  # "w" :: is write permission.
  # "r" :: is read permission.
  # "x" :: is execute permission.
  # "X" ::
  #   is execute permission for directories only, must be used in conjunction with "+"
  # "s" :: is uid, gid.
  # "t" :: is sticky bit.
  # "+" :: is added to a class given the specified mode.
  # "-" :: Is removed from a given class given mode.
  # "=" :: Is the exact nature of the class will be given a specified mode.

  def chmod(mode, list, noop: nil, verbose: nil)
    list = fu_list(list)
    fu_output_message sprintf('chmod %s %s', mode_to_s(mode), list.join(' ')) if verbose
    return if noop
    list.each do |path|
      Entry_.new(path).chmod(fu_mode(mode, path))
    end
  end
  module_function :chmod

  #
  # Changes permission bits on the named files (in +list+)
  # to the bit pattern represented by +mode+.
  #
  #   FileUtils.chmod_R 0700, "/tmp/app.#{$$}"
  #   FileUtils.chmod_R "u=wrx", "/tmp/app.#{$$}"
  #
  def chmod_R(mode, list, noop: nil, verbose: nil, force: nil)
    list = fu_list(list)
    fu_output_message sprintf('chmod -R%s %s %s',
                              (force ? 'f' : ''),
                              mode_to_s(mode), list.join(' ')) if verbose
    return if noop
    list.each do |root|
      Entry_.new(root).traverse do |ent|
        begin
          ent.chmod(fu_mode(mode, ent.path))
        rescue
          raise unless force
        end
      end
    end
  end
  module_function :chmod_R

  #
  # Changes owner and group on the named files (in +list+)
  # to the user +user+ and the group +group+.  +user+ and +group+
  # may be an ID (Integer/String) or a name (String).
  # If +user+ or +group+ is nil, this method does not change
  # the attribute.
  #
  #   FileUtils.chown 'root', 'staff', '/usr/local/bin/ruby'
  #   FileUtils.chown nil, 'bin', Dir.glob('/usr/bin/*'), :verbose => true
  #
  def chown(user, group, list, noop: nil, verbose: nil)
    list = fu_list(list)
    fu_output_message sprintf('chown %s %s',
                              (group ? "#{user}:#{group}" : user || ':'),
                              list.join(' ')) if verbose
    return if noop
    uid = fu_get_uid(user)
    gid = fu_get_gid(group)
    list.each do |path|
      Entry_.new(path).chown uid, gid
    end
  end
  module_function :chown

  #
  # Changes owner and group on the named files (in +list+)
  # to the user +user+ and the group +group+ recursively.
  # +user+ and +group+ may be an ID (Integer/String) or
  # a name (String).  If +user+ or +group+ is nil, this
  # method does not change the attribute.
  #
  #   FileUtils.chown_R 'www', 'www', '/var/www/htdocs'
  #   FileUtils.chown_R 'cvs', 'cvs', '/var/cvs', :verbose => true
  #
  def chown_R(user, group, list, noop: nil, verbose: nil, force: nil)
    list = fu_list(list)
    fu_output_message sprintf('chown -R%s %s %s',
                              (force ? 'f' : ''),
                              (group ? "#{user}:#{group}" : user || ':'),
                              list.join(' ')) if verbose
    return if noop
    uid = fu_get_uid(user)
    gid = fu_get_gid(group)
    list.each do |root|
      Entry_.new(root).traverse do |ent|
        begin
          ent.chown uid, gid
        rescue
          raise unless force
        end
      end
    end
  end
  module_function :chown_R

  begin
    require 'etc'
  rescue LoadError # rescue LoadError for miniruby
  end

  def fu_get_uid(user)   #:nodoc:
    return nil unless user
    case user
    when Integer
      user
    when /\A\d+\z/
      user.to_i
    else
      Etc.getpwnam(user) ? Etc.getpwnam(user).uid : nil
    end
  end
  private_module_function :fu_get_uid

  def fu_get_gid(group)   #:nodoc:
    return nil unless group
    case group
    when Integer
      group
    when /\A\d+\z/
      group.to_i
    else
      Etc.getgrnam(group) ? Etc.getgrnam(group).gid : nil
    end
  end
  private_module_function :fu_get_gid

  #
  # Updates modification time (mtime) and access time (atime) of file(s) in
  # +list+.  Files are created if they don't exist.
  #
  #   FileUtils.touch 'timestamp'
  #   FileUtils.touch Dir.glob('*.c');  system 'make'
  #
  def touch(list, noop: nil, verbose: nil, mtime: nil, nocreate: nil)
    list = fu_list(list)
    t = mtime
    if verbose
      fu_output_message "touch #{nocreate ? '-c ' : ''}#{t ? t.strftime('-t %Y%m%d%H%M.%S ') : ''}#{list.join ' '}"
    end
    return if noop
    list.each do |path|
      created = nocreate
      begin
        File.utime(t, t, path)
      rescue Errno::ENOENT
        raise if created
        File.open(path, 'a') {
          ;
        }
        created = true
        retry if t
      end
    end
  end
  module_function :touch

  private

  module StreamUtils_
    private

    case (defined?(::RbConfig) ? ::RbConfig::CONFIG['host_os'] : ::RUBY_PLATFORM)
    when /mswin|mingw/
      def fu_windows?; true end
    else
      def fu_windows?; false end
    end

    def fu_copy_stream0(src, dest, blksize = nil)   #:nodoc:
      IO.copy_stream(src, dest)
    end

    def fu_stream_blksize(*streams)
      streams.each do |s|
        next unless s.respond_to?(:stat)
        size = fu_blksize(s.stat)
        return size if size
      end
      fu_default_blksize()
    end

    def fu_blksize(st)
      s = st.blksize
      return nil unless s
      return nil if s == 0
      s
    end

    def fu_default_blksize
      1024
    end
  end

  include StreamUtils_
  extend StreamUtils_

  class Entry_   #:nodoc: internal use only
    include StreamUtils_

    def initialize(a, b = nil, deref = false)
      @prefix = @rel = @path = nil
      if b
        @prefix = a
        @rel = b
      else
        @path = a
      end
      @deref = deref
      @stat = nil
      @lstat = nil
    end

    def inspect
      "\#<#{self.class} #{path()}>"
    end

    def path
      if @path
        File.path(@path)
      else
        join(@prefix, @rel)
      end
    end

    def prefix
      @prefix || @path
    end

    def rel
      @rel
    end

    def dereference?
      @deref
    end

    def exist?
      begin
        lstat
        true
      rescue Errno::ENOENT
        false
      end
    end

    def file?
      s = lstat!
      s and s.file?
    end

    def directory?
      s = lstat!
      s and s.directory?
    end

    def symlink?
      s = lstat!
      s and s.symlink?
    end

    def chardev?
      s = lstat!
      s and s.chardev?
    end

    def blockdev?
      s = lstat!
      s and s.blockdev?
    end

    def socket?
      s = lstat!
      s and s.socket?
    end

    def pipe?
      s = lstat!
      s and s.pipe?
    end

    S_IF_DOOR = 0xD000

    def door?
      s = lstat!
      s and (s.mode & 0xF000 == S_IF_DOOR)
    end

    def entries
      opts = {}
      opts[:encoding] = ::Encoding::UTF_8 if fu_windows?
      Dir.children(path, opts)\
          .map {|n| Entry_.new(prefix(), join(rel(), n.untaint)) }
    end

    def stat
      return @stat if @stat
      if lstat() and lstat().symlink?
        @stat = File.stat(path())
      else
        @stat = lstat()
      end
      @stat
    end

    def stat!
      return @stat if @stat
      if lstat! and lstat!.symlink?
        @stat = File.stat(path())
      else
        @stat = lstat!
      end
      @stat
    rescue SystemCallError
      nil
    end

    def lstat
      if dereference?
        @lstat ||= File.stat(path())
      else
        @lstat ||= File.lstat(path())
      end
    end

    def lstat!
      lstat()
    rescue SystemCallError
      nil
    end

    def chmod(mode)
      if symlink?
        File.lchmod mode, path() if have_lchmod?
      else
        File.chmod mode, path()
      end
    end

    def chown(uid, gid)
      if symlink?
        File.lchown uid, gid, path() if have_lchown?
      else
        File.chown uid, gid, path()
      end
    end

    def link(dest)
      case
      when directory?
        if !File.exist?(dest) and descendant_directory?(dest, path)
          raise ArgumentError, "cannot link directory %s to itself %s" % [path, dest]
        end
        begin
          Dir.mkdir dest
        rescue
          raise unless File.directory?(dest)
        end
      else
        File.link path(), dest
      end
    end

    def copy(dest)
      lstat
      case
      when file?
        copy_file dest
      when directory?
        if !File.exist?(dest) and descendant_directory?(dest, path)
          raise ArgumentError, "cannot copy directory %s to itself %s" % [path, dest]
        end
        begin
          Dir.mkdir dest
        rescue
          raise unless File.directory?(dest)
        end
      when symlink?
        File.symlink File.readlink(path()), dest
      when chardev?
        raise "cannot handle device file" unless File.respond_to?(:mknod)
        mknod dest, ?c, 0666, lstat().rdev
      when blockdev?
        raise "cannot handle device file" unless File.respond_to?(:mknod)
        mknod dest, ?b, 0666, lstat().rdev
      when socket?
        raise "cannot handle socket" unless File.respond_to?(:mknod)
        mknod dest, nil, lstat().mode, 0
      when pipe?
        raise "cannot handle FIFO" unless File.respond_to?(:mkfifo)
        mkfifo dest, 0666
      when door?
        raise "cannot handle door: #{path()}"
      else
        raise "unknown file type: #{path()}"
      end
    end

    def copy_file(dest)
      File.open(path()) do |s|
        File.open(dest, 'wb', s.stat.mode) do |f|
          IO.copy_stream(s, f)
        end
      end
    end

    def copy_metadata(path)
      st = lstat()
      if !st.symlink?
        File.utime st.atime, st.mtime, path
      end
      mode = st.mode
      begin
        if st.symlink?
          begin
            File.lchown st.uid, st.gid, path
          rescue NotImplementedError
          end
        else
          File.chown st.uid, st.gid, path
        end
      rescue Errno::EPERM, Errno::EACCES
        # clear setuid/setgid
        mode &= 01777
      end
      if st.symlink?
        begin
          File.lchmod mode, path
        rescue NotImplementedError
        end
      else
        File.chmod mode, path
      end
    end

    def remove
      if directory?
        remove_dir1
      else
        remove_file
      end
    end

    def remove_dir1
      platform_support {
        Dir.rmdir path().chomp(?/)
      }
    end

    def remove_file
      platform_support {
        File.unlink path
      }
    end

    def platform_support
      return yield unless fu_windows?
      first_time_p = true
      begin
        yield
      rescue Errno::ENOENT
        raise
      rescue => err
        if first_time_p
          first_time_p = false
          begin
            File.chmod 0700, path()   # Windows does not have symlink
            retry
          rescue SystemCallError
          end
        end
        raise err
      end
    end

    def preorder_traverse
      stack = [self]
      while ent = stack.pop
        yield ent
        stack.concat ent.entries.reverse if ent.directory?
      end
    end

    alias traverse preorder_traverse

    def postorder_traverse
      if directory?
        entries().each do |ent|
          ent.postorder_traverse do |e|
            yield e
          end
        end
      end
    ensure
      yield self
    end

    def wrap_traverse(pre, post)
      pre.call self
      if directory?
        entries.each do |ent|
          ent.wrap_traverse pre, post
        end
      end
      post.call self
    end

    private

    $fileutils_rb_have_lchmod = nil

    def have_lchmod?
      # This is not MT-safe, but it does not matter.
      if $fileutils_rb_have_lchmod == nil
        $fileutils_rb_have_lchmod = check_have_lchmod?
      end
      $fileutils_rb_have_lchmod
    end

    def check_have_lchmod?
      return false unless File.respond_to?(:lchmod)
      File.lchmod 0
      return true
    rescue NotImplementedError
      return false
    end

    $fileutils_rb_have_lchown = nil

    def have_lchown?
      # This is not MT-safe, but it does not matter.
      if $fileutils_rb_have_lchown == nil
        $fileutils_rb_have_lchown = check_have_lchown?
      end
      $fileutils_rb_have_lchown
    end

    def check_have_lchown?
      return false unless File.respond_to?(:lchown)
      File.lchown nil, nil
      return true
    rescue NotImplementedError
      return false
    end

    def join(dir, base)
      return File.path(dir) if not base or base == '.'
      return File.path(base) if not dir or dir == '.'
      File.join(dir, base)
    end

    if File::ALT_SEPARATOR
      DIRECTORY_TERM = "(?=[/#{Regexp.quote(File::ALT_SEPARATOR)}]|\\z)"
    else
      DIRECTORY_TERM = "(?=/|\\z)"
    end
    SYSCASE = File::FNM_SYSCASE.nonzero? ? "-i" : ""

    def descendant_directory?(descendant, ascendant)
      /\A(?#{SYSCASE}:#{Regexp.quote(ascendant)})#{DIRECTORY_TERM}/ =~ File.dirname(descendant)
    end
  end   # class Entry_

  def fu_list(arg)   #:nodoc:
    [arg].flatten.map {|path| File.path(path) }
  end
  private_module_function :fu_list

  def fu_each_src_dest(src, dest)   #:nodoc:
    fu_each_src_dest0(src, dest) do |s, d|
      raise ArgumentError, "same file: #{s} and #{d}" if fu_same?(s, d)
      yield s, d
    end
  end
  private_module_function :fu_each_src_dest

  def fu_each_src_dest0(src, dest)   #:nodoc:
    if tmp = Array.try_convert(src)
      tmp.each do |s|
        s = File.path(s)
        yield s, File.join(dest, File.basename(s))
      end
    else
      src = File.path(src)
      if File.directory?(dest)
        yield src, File.join(dest, File.basename(src))
      else
        yield src, File.path(dest)
      end
    end
  end
  private_module_function :fu_each_src_dest0

  def fu_same?(a, b)   #:nodoc:
    File.identical?(a, b)
  end
  private_module_function :fu_same?

  @fileutils_output = $stderr
  @fileutils_label  = ''

  def fu_output_message(msg)   #:nodoc:
    @fileutils_output ||= $stderr
    @fileutils_label  ||= ''
    @fileutils_output.puts @fileutils_label + msg
  end
  private_module_function :fu_output_message

  # This hash table holds command options.
  OPT_TABLE = {}    #:nodoc: internal use only
  (private_instance_methods & methods(false)).inject(OPT_TABLE) {|tbl, name|
    (tbl[name.to_s] = instance_method(name).parameters).map! {|t, n| n if t == :key}.compact!
    tbl
  }

  #
  # Returns an Array of method names which have any options.
  #
  #   p FileUtils.commands  #=> ["chmod", "cp", "cp_r", "install", ...]
  #
  def self.commands
    OPT_TABLE.keys
  end

  #
  # Returns an Array of option names.
  #
  #   p FileUtils.options  #=> ["noop", "force", "verbose", "preserve", "mode"]
  #
  def self.options
    OPT_TABLE.values.flatten.uniq.map {|sym| sym.to_s }
  end

  #
  # Returns true if the method +mid+ have an option +opt+.
  #
  #   p FileUtils.have_option?(:cp, :noop)     #=> true
  #   p FileUtils.have_option?(:rm, :force)    #=> true
  #   p FileUtils.have_option?(:rm, :preserve) #=> false
  #
  def self.have_option?(mid, opt)
    li = OPT_TABLE[mid.to_s] or raise ArgumentError, "no such method: #{mid}"
    li.include?(opt)
  end

  #
  # Returns an Array of option names of the method +mid+.
  #
  #   p FileUtils.options_of(:rm)  #=> ["noop", "verbose", "force"]
  #
  def self.options_of(mid)
    OPT_TABLE[mid.to_s].map {|sym| sym.to_s }
  end

  #
  # Returns an Array of method names which have the option +opt+.
  #
  #   p FileUtils.collect_method(:preserve) #=> ["cp", "cp_r", "copy", "install"]
  #
  def self.collect_method(opt)
    OPT_TABLE.keys.select {|m| OPT_TABLE[m].include?(opt) }
  end

  LOW_METHODS = singleton_methods(false) - collect_method(:noop).map(&:intern)
  module LowMethods
    private
    def _do_nothing(*)end
    ::FileUtils::LOW_METHODS.map {|name| alias_method name, :_do_nothing}
  end

  METHODS = singleton_methods() - [:private_module_function,
      :commands, :options, :have_option?, :options_of, :collect_method]

  #
  # This module has all methods of FileUtils module, but it outputs messages
  # before acting.  This equates to passing the <tt>:verbose</tt> flag to
  # methods in FileUtils.
  #
  module Verbose
    include FileUtils
    @fileutils_output  = $stderr
    @fileutils_label   = ''
    names = ::FileUtils.collect_method(:verbose)
    names.each do |name|
      module_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def #{name}(*args, **options)
          super(*args, **options, verbose: true)
        end
      EOS
    end
    private(*names)
    extend self
    class << self
      public(*::FileUtils::METHODS)
    end
  end

  #
  # This module has all methods of FileUtils module, but never changes
  # files/directories.  This equates to passing the <tt>:noop</tt> flag
  # to methods in FileUtils.
  #
  module NoWrite
    include FileUtils
    include LowMethods
    @fileutils_output  = $stderr
    @fileutils_label   = ''
    names = ::FileUtils.collect_method(:noop)
    names.each do |name|
      module_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def #{name}(*args, **options)
          super(*args, **options, noop: true)
        end
      EOS
    end
    private(*names)
    extend self
    class << self
      public(*::FileUtils::METHODS)
    end
  end

  #
  # This module has all methods of FileUtils module, but never changes
  # files/directories, with printing message before acting.
  # This equates to passing the <tt>:noop</tt> and <tt>:verbose</tt> flag
  # to methods in FileUtils.
  #
  module DryRun
    include FileUtils
    include LowMethods
    @fileutils_output  = $stderr
    @fileutils_label   = ''
    names = ::FileUtils.collect_method(:noop)
    names.each do |name|
      module_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def #{name}(*args, **options)
          super(*args, **options, noop: true, verbose: true)
        end
      EOS
    end
    private(*names)
    extend self
    class << self
      public(*::FileUtils::METHODS)
    end
  end

end