The document discusses input/output (IO) and file handling in Ruby. It covers topics like opening files in different modes, reading and writing files, iterating over file lines, and using the Faker gem to generate test data like names and addresses. It also shows examples of working with directories and files, like counting files in a directory and iterating over files with a specific extension.

1. I/O and Files

2. IO: Input/Output IO class is the basis for all input and output in Ruby IO objects represent readable and/or writable connections to disk files, keyboards & screens File is a subclass of IO and allows for reading and writing files in ruby

3. common modes for opening I/O ports "r" Read-only, starts at beginning of file (default) "r+" Read-write, starts at beginning of file "w" Write-only, truncates existing file to zero length or creates a new file for writing "w+" Read-write, truncates existing file to zero length or creates a new file for reading and writing

4. open a file Creating the file object opens the file: >> f = File.new("abc.rb") => #<File:abc.rb>

5. open file – with a block File.open is synonomous with File.new, except that it can take a block: >> File.open(“abc.rb", "r+") do |f| f << "hello" end => #<File:abc.rb (closed)>

6. read a file return a single line >> f.gets => "aaa" return the whole file after current position >> f.read => "aaabbbccc" returns file as an array of lines >> f.readlines => ["aaa", "bbb", "ccc"]

7. position & rewind >> f.rewind => 0 >> f.pos => 0 >> f.gets => "aaa" >> f.pos => 4

8. iterate over lines File objects are enumerable: >> f.each {|line| puts line} aaa bbb ccc

9. use any enumerable method >> f.map {|line| line.chomp + "... "} => ["ddd... ", "eee... ", "fff4th letter to 6th... "] >> f.any? {|line| line =~ /ddd/ } => false >> f.rewind => 0 >> f.any? {|line| line =~ /ddd/ } => true

10. write to a file “r+” argument >> g = File.new("def.rb", "r+") => #<File:def.rb> >> g.read => "dddeeefff" >> g.puts "4th letter to 6th” >> g.rewind >> g.read => "dddeeefff4th letter to 6th"

13. final product: name: Matteo Kuhic street_address: 6413 Timmothy Brook city: Gleichnerhaven state: Florida zip_code: 40554-7199

14. Live Coding markdown to textile conversion, with files

15. directories >> d = Dir.new("/Users/liahhansen/s/dir") => #<Dir:/Users/liahhansen/s/dir> >> d.entries => [".", "..", "abc.rb", "anothersubdir", "def.rb", "ghi.rb", "subdirectory"]

16. count files in directory >> i=0 => 0 >> d.each {|x| i+=1; puts i} 1 2 3 4 5 6 7

17. iterate over files in directory >> ruby_files = Dir["*.rb"] => ["abc.rb", "def.rb", "ghi.rb"] >> ruby_files.map do |file| "rb_" + file end => ["rb_abc.rb", "rb_def.rb", "rb_ghi.rb"]

18. Homework Chapters: 12 Exercises: make index for directory