Ruby File I/O
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The document discusses input/output (IO) and file handling in Ruby. It explains that the IO class is the basis for all input and output, and that the File class allows reading and writing files as it is a subclass of IO. It then provides examples of how to open, read, write, iterate over, and get metadata from files and directories in Ruby.
![read a filereturn a single line>> f.gets=> "aaa\n"return the whole file after current position>> f.read=> "aaa\nbbb\nccc"returns file as an array of lines>> f.readlines=> ["aaa\n", "bbb\n", "ccc"]](https://image.slidesharecdn.com/7filesio-100804092105-phpapp01/85/Ruby-File-I-O-6-320.jpg)
![use any enumerable method>> f.map {|line| line.chomp + "... "}=> [”aaa... ", ”bbb... ", ”ccc... "]>> f.any? {|line| line =~ /aaa\n/ }=> false>> f.rewind=> 0>> f.any? {|line| line =~ /aaa\n/ }=> true](https://image.slidesharecdn.com/7filesio-100804092105-phpapp01/85/Ruby-File-I-O-9-320.jpg)
![directories>> d = Dir.new("/Users/liahhansen/s/dir")=> #<Dir:/Users/liahhansen/s/dir>>> d.entries=> [".", "..", "abc.rb", "anothersubdir", "def.rb", "ghi.rb", "subdirectory"]](https://image.slidesharecdn.com/7filesio-100804092105-phpapp01/85/Ruby-File-I-O-11-320.jpg)
![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"]](https://image.slidesharecdn.com/7filesio-100804092105-phpapp01/85/Ruby-File-I-O-13-320.jpg)
Ruby File I/O
- 1. I/O and Filesby Liah Hansen and Sarah Allen
- 2. IO: Input/OutputIO class is the basis for all input and output in RubyIO 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 fileCreating the file object opens the file: >> f = File.new("abc.rb")=> #<File:abc.rb>
- 5. open file – with a blockFile.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 filereturn a single line>> f.gets=> "aaa\n"return the whole file after current position>> f.read=> "aaa\nbbb\nccc"returns file as an array of lines>> f.readlines=> ["aaa\n", "bbb\n", "ccc"]
- 7. position & rewind>> f.rewind=> 0>> f.pos=> 0>> f.gets=> "aaa\n">> f.pos=> 4
- 8. iterate over linesFile objects are enumerable:>> f.each {|line| puts line}aaabbbccc
- 9. use any enumerable method>> f.map {|line| line.chomp + "... "}=> [”aaa... ", ”bbb... ", ”ccc... "]>> f.any? {|line| line =~ /aaa\n/ }=> false>> f.rewind=> 0>> f.any? {|line| line =~ /aaa\n/ }=> true
- 10. write to a file“w+” argument>>my_file= File.new("data.txt", "w+")=> #<File:def.rb>>> my_file.write("something")=> 9>> my_file.rewind=> 0>> my_file.read=> "something"
- 11. directories>> d = Dir.new("/Users/liahhansen/s/dir")=> #<Dir:/Users/liahhansen/s/dir>>> d.entries=> [".", "..", "abc.rb", "anothersubdir", "def.rb", "ghi.rb", "subdirectory"]
- 12. count files in directory>> i=0=> 0>> d.each {|x| i+=1; puts i}1234567
- 13. 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"]