# Unexpected sprintf/String % Behavior **URL:** \ **Category:** ruby-talk\ **Created:** [15 June 2005 16:49 UTC](https://rubytalk.org/t/unexpected-sprintf-string-behavior/18988 "2005-06-15T16:49:25Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Ben\_Gribaudo1](https://avatars.discourse-cdn.com/v4/letter/b/e47c2d/32.png) [@Ben\_Gribaudo1](https://rubytalk.org/u/Ben_Gribaudo1)\ **Post date:** [15 June 2005 16:49 UTC](https://rubytalk.org/t/unexpected-sprintf-string-behavior/18988/1 "2005-06-15T16:49:25Z")
Hello, I am puzzled by some strange (to me) behavior exhibited by String's % method as well as sprintf. Both "%02d" % "07" and sprintf("%02d","07") output "07". However, "%02d" % "08" and sprintf("%02d","08") both raise 'ArgumentError: invalid value for Integer: "08"'. Why does a string of "07" work while "08" does not? This is true when I test this on a MS Windows XP Pro box running Ruby 1.6.8 and when I test it on a Debian Woody box (kernal 2.4.19) running Ruby 1.8.2. IRB examples and results are below. Thank you, Ben Win XP box > **···** > > ------------- > irb(main):014:0\> "%02d" % "07" > =\> "07" > irb(main):015:0\> "%02d" % "08" > ArgumentError: invalid value for Integer: "08" >         from (irb):15:in `%' >         from (irb):15 > irb(main):017:0\> sprintf("%02d","07") > =\> "07" > irb(main):018:0\> sprintf("%02d","08") > ArgumentError: invalid value for Integer: "08" >         from (irb):18:in `sprintf' >         from (irb):18 > > Linux box > ---------- > irb(main):003:0\> "%02d" % "07" > =\> "07" > irb(main):004:0\> "%02d" % "08" > ArgumentError: invalid value for Integer: "08" >         from (irb):4:in `%' >         from (irb):4 > > irb(main):005:0\> sprintf("%02d","07") > =\> "07" > irb(main):006:0\> sprintf("%02d","08") > ArgumentError: invalid value for Integer: "08" >         from (irb):6:in `sprintf' >         from (irb):6 ---
**Author:** ![Gennady1](https://avatars.discourse-cdn.com/v4/letter/g/a4c791/32.png) [@Gennady1](https://rubytalk.org/u/Gennady1)\ **Post date:** [15 June 2005 16:58 UTC](https://rubytalk.org/t/unexpected-sprintf-string-behavior/18988/2 "2005-06-15T16:58:25Z")
Ben Gribaudo wrote: > Hello, > > I am puzzled by some strange (to me) behavior exhibited by String's % method as well as sprintf. Both "%02d" % "07" and sprintf("%02d","07") output "07". However, "%02d" % "08" and sprintf("%02d","08") both raise 'ArgumentError: invalid value for Integer: "08"'. Why does a string of "07" work while "08" does not? Because leading 0 makes your argument string be interpreted as an octal number, where '8' is not a valid digit (0..7 are valid in base 8). Hope it helps. Gennady. ---
**Author:** ![Ara.T.Howard6](https://avatars.discourse-cdn.com/v4/letter/a/958977/32.png) [@Ara.T.Howard6](https://rubytalk.org/u/Ara.T.Howard6)\ **Post date:** [15 June 2005 16:58 UTC](https://rubytalk.org/t/unexpected-sprintf-string-behavior/18988/3 "2005-06-15T16:58:45Z")
leading zeros (as in c) mean octal. so there is no 08. only    00 01 02 03 04 05 06 07 the number eight being 10 for instance    harp:~ \> irb    irb(main):001:0\> 010    =\> 8    irb(main):002:0\> 017    =\> 15    irb(main):003:0\> 08    SyntaxError: compile error    (irb):3: Illegal octal digit            from (irb):3 not that you also have hex and binary literals like    0xa    0b101010 hth. -a > **···** > > On Thu, 16 Jun 2005, Ben Gribaudo wrote: > > > Hello, > > > > I am puzzled by some strange (to me) behavior exhibited by String's % method as well as sprintf. Both "%02d" % "07" and sprintf("%02d","07") output "07". However, "%02d" % "08" and sprintf("%02d","08") both raise 'ArgumentError: invalid value for Integer: "08"'. Why does a string of "07" work while "08" does not? > > # -- > > > email :: ara [dot] t [dot] howard [at] noaa [dot] gov > > phone :: 303.497.6469 > > My religion is very simple. My religion is kindness. > > --Tenzin Gyatso > > =============================================================================== ---
**Author:** ![Ben\_Gribaudo1](https://avatars.discourse-cdn.com/v4/letter/b/e47c2d/32.png) [@Ben\_Gribaudo1](https://rubytalk.org/u/Ben_Gribaudo1)\ **Post date:** [17 June 2005 19:11 UTC](https://rubytalk.org/t/unexpected-sprintf-string-behavior/18988/4 "2005-06-17T19:11:35Z")
Thank you for explaining this. Ben