Ruby is one of the growing scripting & web development language, it was designed to be easy to learn and provides least possible surprises for a newcomer to the language. Ruby on Rails is a very popular and robust MVC web framework. Ruby can also be used as CGI or can be inserted into Apache as module with the help of mod_ruby. Ruby comes in many variants, but let's leave the details of that for another day, in this article we'll discuss how the basic input/output operations such a reading from the terminal, file, writing out to a file etc. can be done in Ruby. Reading from STDIN Ruby has a built-in function gets() which reads a line from a file handle, in this case the STDIN. Now, let's look at a simple code which will read a line from the STDIN and print it. Code: #!/usr/bin/ruby # "print" because puts adds a trailing newline print "Enter your name: " # read a line into the variable name name = gets # print puts "Hello, #{name}" Output: Code: [pradeep@desktop]$ ./test.rb Enter your name: Pradeep Hello, Pradeep Let's look at another example where we'll ready the whole input line by line and print it's length. Code: #!/usr/bin/ruby string = '' while line = gets string = string + line end puts "Input was " + string.length.to_s + " character(s) long" Output: Code: [pradeep@desktop]$ ./test.rb The Quick Brown Fox Jumps Over The Lazy Dog Wow that was quick Input was 63 character(s) long [pradeep@desktop]$ ./test.rb < test.rb Input was 140 character(s) long Reading From A File The File object is contains the related operations for opening a file which returns the file handle object. Please follow the example below. Code: #!/usr/bin/ruby # open the file for reading file_h = File.new("data.txt", "r") # iterate till eof while line = file_h.gets puts line end # close the filehandle file_h.close Now, let me list a few file handle iterators which are unique to Ruby in the next example. Code: #!/usr/bin/ruby # open the file for reading file_h = File.new("data.txt", "r") # the each_byte method, reads character by character file_h.each_byte { |ch| putc ch } # the each_line method, reads line by line, default line separator is newline file_h.each_line { |line| puts "Read #{line.dump}" } # specify a different line separator file_h.each_line("|") do |line| puts "Read #{ line.dump }" end # reading a specific no. of bytes, say reading 16 bytes data = file_h.sysread(16) # read the whole file into an array file_array = IO.readlines("data.txt") Writing To A File Writing to files with Ruby can be more fun than other languages, I guess it's because everything in Ruby is an object. There are numerous methods available to write to a file like print, printf, puts, syswrite, etc. all are called on the file handle. But remember not to mix syswrite and other methods, as syswrite works on a system level and is unbuffered, else set the file handle to be unbuffered by default. Now, follow the example below. Code: #!/usr/bin/ruby # open the file for writing, you can also open it for appending with "a" # you may also specify the Unix file permissions for a new that would be created file_fh = File.new('data.txt','w+', 0644) # set the file handle to turn of buffering, i.e. it will immediately write to the file file_fh.sync = true # write with puts, it'll append a newline in the end file_fh.puts("My first line") # write with print, it'll not add a newline file_fh.print("Add with print") # to see that there wasn't any newline added file_fh.print("Add with another print") # write any arbitrary string with syswrite, syswrite is faster than other methods # it returns the number of bytes written puts file_fh.syswrite("Trying syswrite") # remember to close the file, specially in case of buffered mode so that # any unbuffered data is written to the disk file_fh.close Hope this was helpful, enjoy coding in Ruby.
