# Sprintf bug (?) **URL:** \ **Category:** Ruby\ **Created:** [November 11, 2006, 7:30pm UTC](https://www.ruby-forum.com/t/sprintf-bug/75635 "2006-11-11T19:30:15Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 11, 2006, 7:30pm UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/1 "2006-11-11T19:30:15Z")
Hello all, I am wondering if I have just found a bug in (s)printf… According to the PickAxe, table “sprintf flag characters”: ================= snip ================================== 0 (zero) all Pad with zeros, not spaces. ================= snip ================================== so I think this call irb(main):053:0\> sprintf(“%05s”, 123) =\> " 123" should correctly result in “00123” or I am getting something wrong? thanks, Peter \_\_ [http://www.rubyrailways.com](http://www.rubyrailways.com) ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 11, 2006, 7:50pm UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/2 "2006-11-11T19:50:18Z")
Peter S. wrote: > ================= snip ================================== > or I am getting something wrong? > I think ruby follows the C standard, which says zero padding only > applies to numeric formats. ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 12, 2006, 10:21pm UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/3 "2006-11-12T22:21:20Z")
----- Original Message ----- From: “Peter S.” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) To: “ruby-talk ML” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Sent: Saturday, November 11, 2006 1:28 PM Subject: sprintf bug (?) > ================= snip ================================== > > so I think this call > > irb(main):053:0\> sprintf(“%05s”, 123) > =\> " 123" > > should correctly result in > > “00123” sprintf(“%05d”,123) # ‘d’ not ‘s’ =\> “00123” ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 12, 2006, 10:45pm UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/4 "2006-11-12T22:45:28Z")
Bernard K. wrote: > > irb(main):053:0\> sprintf(“%05s”, 123) > > =\> " 123" > > > > should correctly result in > > > > “00123” > > sprintf(“%05d”,123) # ‘d’ not ‘s’ > =\> “00123” 🙂 I know ‘d’ is not ‘s’, it was a bad example. It should have been irb(main):002:0\> sprintf(“%10s”,‘hello’) =\> " hello" (there are no zeroes…) Peter \_\_ [http://www.rubyrailways.com](http://www.rubyrailways.com) ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 13, 2006, 12:35am UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/5 "2006-11-13T00:35:38Z")
Hi, In message “Re: sprintf bug (?)” on Mon, 13 Nov 2006 07:03:44 +0900, Timothy H. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes: |Possibly you meant “%010s” instead of “%10s”? In any case, I checked the |output of a C program compiled with gcc on my Powerbook running OS X |10.8. In this case, the ‘0’ flag adds padding on the left: This is platform dependent. Linux manpage says: ``` 0 The value should be zero padded. For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, the converted value is padded on the left with zeros rather than blanks. If the 0 and - flags both appear, the 0 flag is ignored. If a precision is given with a numeric conversion (d, i, o, u, x, and X), the 0 flag is ignored. For other conversions, the behavior is ~~~~~~~~~~~~~~~ undefined. ~~~~~~~~~ ``` zero option affects some specifiers. %s is not among them. ``` matz. ``` ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 13, 2006, 8:06am UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/6 "2006-11-13T08:06:09Z")
Yukihiro M. wrote: > zero option affects some specifiers. %s is not among them. Thank, Matz. This made it really clear at last… Peter \_\_ [http://www.rubyrailways.com](http://www.rubyrailways.com) ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 12, 2006, 11:05pm UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/7 "2006-11-12T23:05:29Z")
Peter S. wrote: > > > so I think this call > > > =\> “00123” Possibly you meant “%010s” instead of “%10s”? In any case, I checked the output of a C program compiled with gcc on my Powerbook running OS X 10.8. In this case, the ‘0’ flag adds padding on the left: ruby$ cat testit.c #include \ int main(int argc, char \*argv[]) { printf("%010s", “hello\n”); return 0; } ruby$ ./testit 0000hello ruby$ ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 14, 2006, 2:45am UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/8 "2006-11-14T02:45:27Z")
----- Original Message ----- From: “Yukihiro M.” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) To: “ruby-talk ML” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Sent: Sunday, November 12, 2006 6:34 PM Subject: Re: sprintf bug (?) > This is platform dependent. Linux manpage says: > ~~~~~~~~~ > > zero option affects some specifiers. %s is not among them. > > matz. I suggest that the OP asks ruby’s description of sprintf via “ri sprintf” … it is essentially as described above ---
**Author:** ![splattael](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@splattael](https://www.ruby-forum.com/u/splattael)\ **Post date:** [November 14, 2006, 2:19am UTC](https://www.ruby-forum.com/t/sprintf-bug/75635/9 "2006-11-14T02:19:24Z")
----- Original Message ----- From: “Peter S.” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) To: “ruby-talk ML” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Sent: Sunday, November 12, 2006 4:43 PM Subject: Re: sprintf bug (?) > > > so I think this call > > 🙂 I know ‘d’ is not ‘s’, it was a bad example. It should have been > > irb(main):002:0\> sprintf(“%10s”,‘hello’) > =\> " hello" > > (there are no zeroes…) > > Peter This is the correct behavior of sprintf for strings