Extracting the last n characters from a ruby string

Question

To get the last n characters from a string, I assumed you could use

ending = string[-n..-1]

but if the string is less than

Answer 1

In straight Ruby (without Rails), you can do

string.chars.last(n).join

For example:

2.4.1 :009 > a = 'abcdefghij'
 => "abcdefghij"
2.4.1 :010 > a.chars.last(5).join
 => "fghij"
2.4.1 :011 > a.chars.last(100).join
 => "abcdefghij"

If you're using Ruby on Rails, you can call methods first and last on a string object. These methods are preferred as they're succinct and intuitive.

For example:

[1] pry(main)> a = 'abcdefg'                                                                                                                
 => "abcdefg"
[2] pry(main)> a.first(3)                                                                                                                   
 => "abc"
[3] pry(main)> a.last(4)                                                                                                                    
 => "defg"

Answer 2

Well, the easiest workaround I can think of is:

ending = str[-n..-1] || str

(EDIT: The or operator has lower precedence than assignment, so be sure to use || instead.)

Answer 3

You can use the following code:

string[string.length-n,string.length]

Answer 4

Have you tried a regex?

string.match(/(.{0,#{n}}$)/)
ending=$1

The regex captures as many characters it can at the end of the string, but no more than n. And stores it in $1.

Answer 5

Improvement on EmFi's answer.

string[/.{,#{n}}\z/m]

Answer 6

ending = string.reverse[0...n].reverse