A super basic RFuse file system.

myfs.rb

#!/usr/bin/env ruby
#
# Minus the logging, this is the simplest file system that's most likely
# possible with RFuse-NG. It presents a single directory level that stores
# the contents of files in a Hash.
#
# This is in the public domain.
#
# Enjoy,
# sneakin
#
require 'rfuse_ng'
require 'ostruct'

class LoggedOStruct < OpenStruct
  def method_missing(mid, *args, &block)
    $stderr.puts "#{self}\t#{mid}\t#{args.inspect}" unless mid.to_s =~ /=$/
    super
  end
end

class MyFS < RFuse::Fuse
  def initialize(mnt_pnt, options, libopt)
    super(mnt_pnt, options, libopt)
    @files = Hash.new
    @files['hello.txt'] = "Hello world\n"
  end

  def readdir(ctx, path, filler, offset, ffi)
    $stderr.puts "readdir: #{path} #{offset}"
    if path == '/'
      @files.each do |path, data|
	filler.push(path, create_stat(false, data.length), 0)
      end
    else
      raise Errno::ENOTDIR.new(path)
    end
  end

  def getattr(ctx, path)
    $stderr.puts "Getattr: #{path}\t#{@files.has_key?(File.basename(path))}"
    if path == '/' || @files.has_key?(File.basename(path))
      data = @files[File.basename(path)]
      create_stat(path == '/', data ? data.length : 0 )
    else
      raise Errno::ENOENT.new
    end
  end

  def read(ctx, path, size, offset, fi)
    d = @files.fetch(File.basename(path)) { "" }
    return d[offset..offset + size - 1]
  end

  def write(ctx, path, buf, offset, fi)
    d = @files[File.basename(path)]
    d[offset..offset + buf.length - 1] = buf
    return buf.length
  end

  def mknod(ctx, path, mode, dev)
    @files[File.basename(path)] = String.new
  end

  def unlink(ctx, path)
    $stderr.puts "unlink\t#{path}"
    @files.delete(File.basename(path))
  end

  def rename(ctx, path, as)
    $stderr.puts "rename\t#{path}\t#{as}"
    @files[File.basename(as)] = @files.delete(File.basename(path))
  end

  def truncate(ctx, path, offset)
    $stderr.puts "truncate\t#{path}\t#{offset}"
    @files[File.basename(path)] = @files[File.basename(path)][0..offset]
  end

  def statfs(ctx, path)
    print "statfs: #{path}\n"
    d = LoggedOStruct.new
    d.f_bsize = 0
    d.f_frsize = 0
    d.f_blocks = 0
    d.f_bfree = 0
    d.f_bavail = 0
    d.f_files = @files.size
    d.f_ffree = 0
    d.f_favail = 0
    d.f_fsid = 0
    d.f_flag = 0
    d.f_namemax = 0
    d
  end

  def init(ctx, conn_info)
    print "Starting...\n"
  end

  private

  def create_stat(is_dir = false, size = 0)
    mode = 0666
    if is_dir
      mode = 0777
      mode |= (4 << 12)
    else
      mode |= (8 << 12)
    end
    LoggedOStruct.new(:uid => 1, :gid => 1, :mode => mode, :size => size, :ctime => 0, :atime => Time.now.to_i, :mtime => 0, :dev => 0, :ino => 0, :nlink => is_dir ? 2 : 1, :rdev => 0, :blksize => 0, :blocks => 0)
  end
end

if __FILE__ == $0
  fo = MyFS.new(ARGV[0],["notparsed","-o notparsed,allow_other,volname=MyFS"],["debug"]);

  #kernel:  default_permissions,allow_other,kernel_cache,large_read,direct_io
  #         max_read=N,fsname=NAME
  #library: debug,hard_remove

  Signal.trap("TERM") do
    fo.exit
    fo.unmount
  end

  begin
    fo.loop
  rescue
    print "Error:" + $!
  end
end