what is the best way to remove the last n characters of a string (in Ruby)?

Question

in Ruby, I just want to get rid of the last n characters of a string, but the following doesn't work

"string"[0,-3]

nor

"string".slice(0, -3)

I'd like a clean method, not anything like

"string".chop.chop.chop

it may be trivial, please anyone teach me! thanks!

+1 for `chop.chop.chop`. Makes me think of you as taking an axe to the end of the string. :-) — Donal Fellows, Jun 17 '10 at 07:56
`chop.chop.chop` has the added disadvantage of making three extra copies of your `String`. If it's just `"hello, world"`, then that won't matter, but if it's `File.read('/some/really/big.file')`, it will. — James A. Rosen, Jun 17 '10 at 14:12
The opposite task, getting the last `n` bytes/characters/whatever from your string is slightly tricky: http://stackoverflow.com/questions/2174767/extracting-the-last-n-characters-from-a-ruby-string — Andrew Grimm, Jun 18 '10 at 01:10
See also: [Ruby, remove last N characters from a string?](http://stackoverflow.com/q/4209384/1591669) — unor, Sep 25 '15 at 01:23

score 27 · Accepted Answer · answered Jun 17 '10 at 07:54

27

You can use ranges.

"string"[0..-4]

answered Jun 17 '10 at 07:54

August Lilleaas

You beat me to it! You can also do this with slice: "string".slice(0..-4) – sosborn Jun 17 '10 at 07:58
hi, thanks! I just found that I made a mistake on the second parameter of [ ] or slice; it is length rather than the ending position... – Tao Jun 17 '10 at 08:13
3

Careful! In Ruby 1.8, this *does not* remove the last characters, it removes the last *bytes*! – Jörg W Mittag Jun 17 '10 at 10:59
this answer should explain the parameters. – Tom Carchrae Oct 02 '14 at 14:09

score 9 · Answer 2 · answered Jun 17 '10 at 11:34

9

You could use a regex with gsub ...

"string".gsub( /.{3}$/, '' )

answered Jun 17 '10 at 11:34

irkenInvader

score 1 · Answer 3 · answered Jun 28 '13 at 13:28

1

If you add an ! to slice it will destructively remove the last n characters without having to assign it to another variable:

my_string.slice!(my_string.length-3,my_string.length)

compared to:

new = my_string.slice(0..-4)

answered Jun 28 '13 at 13:28

Blake Erickson

3 Answers3