# Sprintf bug?

**URL:** <https://www.ruby-forum.com/t/sprintf-bug/127769>\
**Category:** Ruby\
**Created:** [February 1, 2008, 4:53am UTC](https://www.ruby-forum.com/t/sprintf-bug/127769 "2008-02-01T04:53:51Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Daniel\_DeLorme](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/9d8465/32.png) [@Daniel\_DeLorme](https://www.ruby-forum.com/u/Daniel_DeLorme)\
**Post date:** [February 1, 2008, 4:53am UTC](https://www.ruby-forum.com/t/sprintf-bug/127769/1 "2008-02-01T04:53:51Z")

</div>

I’ve just stumbled across the following:

machine1$ ruby -ve ‘printf("(%\*-s)\n", 10,“hello”)’  
ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-freebsd6]  
(hello )

machine2$ ruby -ve ‘printf("(%\*-s)\n", 10,“hello”)’  
ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-freebsd6]  
-e:1:in `printf’: flag after width (ArgumentError)  
from -e:1

I can fix it by changing the pattern to “%-\*s”, but is that a bug in  
patchlevel 111 or is it a “bugfix” for a syntax that was never supposed  
to be valid? And if the second case, what is the point of making things  
more restrictive?

Daniel

---

<div class="post-metadata">

**Author:** ![Daniel\_DeLorme](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/9d8465/32.png) [@Daniel\_DeLorme](https://www.ruby-forum.com/u/Daniel_DeLorme)\
**Post date:** [February 1, 2008, 10:09am UTC](https://www.ruby-forum.com/t/sprintf-bug/127769/2 "2008-02-01T10:09:17Z")

</div>

2008/2/1, Daniel DeLorme [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> I can fix it by changing the pattern to “%-\*s”, but is that a bug in  
> patchlevel 111 or is it a “bugfix” for a syntax that was never supposed  
> to be valid?

AFAIK valid syntax always has been this:

irb(main):002:0\> sprintf “%\*s”, 10, “hello”  
=\> " hello"  
irb(main):003:0\> sprintf “%-\*s”, 10, “hello”  
=\> "hello "

So, it’s a bugfix.

> And if the second case, what is the point of making things  
> more restrictive?

I do not understand the question: if it is a bug fix then the new  
behavior is the one that was originally intended. Code that employs  
other syntax is simply broken.

Cheers

robert