HelloWorld.rb

 puts "Hello, World!"

Ruby Online Compiler

Write, Run & Share Ruby code online using OneCompiler's Ruby online compiler for free. It's one of the robust, feature-rich online compilers for Ruby language, running on the latest version 2.3.1. Getting started with the OneCompiler's Ruby compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as Ruby and start coding.

Read input from STDIN in Ruby

OneCompiler's Ruby online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample Ruby program which takes name as input and prints hello message with your name.

name = gets.chomp               
print "Hello #{name}.\n"

About Ruby

Ruby is a general purpose object oriented programming language developed by Yukihiro Matsumoto.

Key features

More commonly used in Rails applications.
Concise and simple to read and powerful too.
Open-source
Expressive features and visual appearance
Flexible language

Syntax help

Data types

Data type	Description	Usage
Fixnum	Represents normal numbers	x = 10
Bignum	Represents big numbers	x =9999999999
Float	Represents decimal numbers	x = 3.14
Complex	Represents imaginary numbers	x = 1 + 2i
Rational	Represents fractional numbers	x = 1/4
BigDecimal	Represents precision decimal numbers	x=1.0
Hash	Represents key value pairs	{"Website"=>"onecompiler","message" => "Happy learning"}

Variables

In Ruby, there is no need to explicitly declare variables to reserve memory space. When you assign a value to a variable, declaration happens automatically and a prefix is needed to indicate the following variable types.

Variable type	Description
Local variables	Scope is limited to the block of the variable initialization. Variable name must start with either `_` or lowercase letter.
Class variables	Class variables belongs to whole class and can be accessible anywhere inside the class. Variable name must start with `@@`. They must be initialized before use.
Instance variables	Instance variables belongs to a instance of the class. They can be accessed from any instance of the class within a method. Variable name must start `@`
Global variables	Scope is global and hence they can be accessible anywhere in the program. Variable name must start with `$`

Loops and conditional statements

1. If family:

If, If-else, Nested-Ifs are used when you want to perform a certain set of operations based on conditional expressions.

If

if(conditional-expression)
    #code    
end

If-else

if(conditional-expression)  
    #code if condition is true  
else   
    #code if condition is false  
end

Nested-If-else

if(condition-expression1)   
    #code if above condition is true  
 elsif(condition-expression2)  
    #code if above condition is true  
elsif(condition-expression3)   
    #code if above condition is true  
...  
else   
    #code if all the conditions are false  
end

2. Case:

Case is similar to Switch statement, where it is used to execute one set of a statement from multiple conditions.

case expression  
[when expression [, expression ...] [then]  
   # code ]...  
[else  
   # code ]  
end

3. For:

For loop is used to iterate a set of statements based on a condition.

for variable in expression do   
  # code  
end

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while condition do   
 # code 
end

5. Do-while:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

loop do   
  #code  
  break if conditional-expression  
end