Ruby p vs puts vs print
Ruby has three useful methods for printing information to the command line:
Kernel#p, Kernel#print and Kernel#puts.
Fire up irb and follow along!
> class P
> def inspect(); "P#inspect"; end
> def to_s(); "P#to_s"; end
> end
> q = P.new
Kernel#print is the simplest of printing methods. print calls to_s on the
object and spits it out to $stdout.
> print q
P#to_s => nil
print does not append a new line.
> print 1,2,3
123 => nil
New lines must be added manually when using print.
> print 1,"\n",2,"\n",3,"\n"
1
2
3
=> nil
puts
Kernel#puts is probably the most common printing methods known to Rubyists.
puts is similar to print – calling to_s – but adds a newline to the output.
> puts q
P#to_s
=> nil
> puts 1,2,3
1
2
3
=> nil
p
Kernel#p is less well known than print and puts.
It is similar to puts in that it adds a newline, but rather than calling to_s, p calls inspect.
> p q
P#inspect
=> P#inspect
> p 1,2,3
1
2
3
=> [1, 2, 3]
p can be more useful for debugging. As puts calls to_s, you can’t be exactly sure of what class an object is.
> puts 1
1
=> nil
> puts '1'
1
=> nil
With p we get a better indicator of what we’re actually looking at.
> p 1
1
=> 1
> p '1'
"1"
=> "1"