# \[C ext to Ruby\] how to output a octal coded number? **URL:** \ **Category:** ruby-talk\ **Created:** [14 August 2007 08:49 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883 "2007-08-14T08:49:56Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![unbewusst](https://avatars.discourse-cdn.com/v4/letter/u/ba9def/32.png) [@unbewusst](https://rubytalk.org/u/unbewusst)\ **Post date:** [14 August 2007 08:49 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/1 "2007-08-14T08:49:56Z")
i write a C extension to Ruby, some methods are dealing with octal number (bytes in english ?) for the file permission : ie something like that : 0777 or 0644 the first 0 (zero) meaning the following is a number coded in octal. that's OK for input of octal number if for example, from ruby the user write : this\_file.perms = 0777 (then with the first 0) i get the right number however, for the time being, i'm returning, for the same value : 777 instead of 0777 when the user wants to read the perms, then my question how to return within a C est to Ruby an integer coded in octal ??? thought, at that time i'm usinbg INT2FIX ( ) best Yvon ---
**Author:** ![Eric\_Hodel1](https://avatars.discourse-cdn.com/v4/letter/e/a9adbd/32.png) [@Eric\_Hodel1](https://rubytalk.org/u/Eric_Hodel1)\ **Post date:** [14 August 2007 09:31 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/2 "2007-08-14T09:31:50Z")
The easiest way will probably be to use sprintf. From C, use rb\_f\_sprintf. > **···** > > On Aug 14, 2007, at 01:49, unbewust wrote: > > > i write a C extension to Ruby, some methods are dealing with octal > > number (bytes in english ?) for the file permission : > > > > ie something like that : > > > > 0777 or 0644 the first 0 (zero) meaning the following is a number > > coded in octal. > > > > that's OK for input of octal number if for example, from ruby the user > > write : > > > > this\_file.perms = 0777 (then with the first 0) > > > > i get the right number > > > > however, for the time being, i'm returning, for the same value : > > > > 777 instead of 0777 when the user wants to read the perms, then my > > question how to return within a C est to Ruby an integer coded in > > octal ??? > > > > thought, at that time i'm usinbg INT2FIX ( ) > > -- > Poor workers blame their tools. Good workers build better tools. The > best workers get their tools to do the work for them. -- Syndicate Wars ---
**Author:** ![Tim\_Pease](https://avatars.discourse-cdn.com/v4/letter/t/3e96dc/32.png) [@Tim\_Pease](https://rubytalk.org/u/Tim_Pease)\ **Post date:** [14 August 2007 14:07 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/3 "2007-08-14T14:07:23Z")
Ruby displays integers in base 10 format. I do not believe there is a way to get it to display 511 in octal (0777) without using sprintf as Eric Hodel mentioned in his reply. However, if you just want to return from a C function and have the number look pretty in your C source code, then this will work: return INT2FIX( 0777 ); But I am not sure if that is what you mean? Blessings, TwP > **···** > > On 8/14/07, unbewust \ wrote: > > > 777 instead of 0777 when the user wants to read the perms, then my > > question how to return within a C est to Ruby an integer coded in > > octal ??? > > > > thought, at that time i'm usinbg INT2FIX ( ) ---
**Author:** ![Simon\_Krahnke](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Simon\_Krahnke](https://rubytalk.org/u/Simon_Krahnke)\ **Post date:** [14 August 2007 15:04 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/4 "2007-08-14T15:04:59Z")
\* unbewust \ (10:46) schrieb: > that's OK for input of octal number if for example, from ruby the user > write : > > this\_file.perms = 0777 (then with the first 0) > > i get the right number > > however, for the time being, i'm returning, for the same value : > 777 instead of 0777 when the user wants to read the perms, then my > question how to return within a C est to Ruby an integer coded in > octal ??? A integer in ruby is a numeric value, it's not octal or decimal. > thought, at that time i'm usinbg INT2FIX ( ) A string representation of a number can be octal or decimal or whatever. The Ruby as well and the C library have means to convert between numbers and its string representations. num = "775".to\_i(8) dec = num.to\_s #\> "509" oct = num.to\_s(8) #\> "775" mfg, simon .... l > best > > Yvon BTW: The german word unbewusst is written with two s. 🙂 ---
**Author:** ![unbewusst](https://avatars.discourse-cdn.com/v4/letter/u/ba9def/32.png) [@unbewusst](https://rubytalk.org/u/unbewusst)\ **Post date:** [14 August 2007 12:59 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/5 "2007-08-14T12:59:59Z")
OK, thanks, but i don't want to print it just have it as a return value then you mean i can use sprintf to print to stdout and the value will be cached by Ruby ? this is for cosmetic purpose because my "octal" is well writen except the first "0" (zero) missing... > **···** > > On 14 août, 11:31, Eric Hodel \ wrote: > > > On Aug 14, 2007, at 01:49, unbewust wrote: > > > > \> i write a C extension to Ruby, some methods are dealing with octal > > \> number (bytes in english ?) for the file permission : > > > > \> ie something like that : > > > > \> 0777 or 0644 the first 0 (zero) meaning the following is a number > > \> coded in octal. > > > > \> that's OK for input of octal number if for example, from ruby the user > > \> write : > > > > \> this\_file.perms = 0777 (then with the first 0) > > > > \> i get the right number > > > > \> however, for the time being, i'm returning, for the same value : > > > > \> 777 instead of 0777 when the user wants to read the perms, then my > > \> question how to return within a C est to Ruby an integer coded in > > \> octal ??? > > > > \> thought, at that time i'm usinbg INT2FIX ( ) > > > > The easiest way will probably be to use sprintf. From C, use > > rb\_f\_sprintf. > > > > -- > > Poor workers blame their tools. Good workers build better tools. The > > best workers get their tools to do the work for them. -- Syndicate Wars ---
**Author:** ![unbewusst](https://avatars.discourse-cdn.com/v4/letter/u/ba9def/32.png) [@unbewusst](https://rubytalk.org/u/unbewusst)\ **Post date:** [14 August 2007 15:35 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/6 "2007-08-14T15:35:04Z")
> \* unbewust \ (10:46) schrieb: > > \> that's OK for input of octal number if for example, from ruby the user > \> write : > > \> this\_file.perms = 0777 (then with the first 0) > > \> i get the right number > > \> however, for the time being, i'm returning, for the same value : > \> 777 instead of 0777 when the user wants to read the perms, then my > \> question how to return within a C est to Ruby an integer coded in > \> octal ??? > > A integer in ruby is a numeric value, it's not octal or decimal. > > \> thought, at that time i'm usinbg INT2FIX ( ) > > A string representation of a number can be octal or decimal or whatever. > The Ruby as well and the C library have means to convert between numbers > and its string representations. OK thanks the reason for me to output as an octal number it is an habit when talking about perms... i'll look at the C library to output that the correct way. > num = "775".to\_i(8) > dec = num.to\_s #\> "509" > oct = num.to\_s(8) #\> "775" i've allready a way to output my number as an octal "775" BUT i'll like having better "0775" because in the C language the first 0 means octal and i ask for xhen input . > mfg, simon .... l > > \> best > > \> Yvon > > BTW: The german word unbewusst is written with two s. 🙂 yes i know, i didn't cacht my misspelling 😉 vielen dank 😉 Yvon > **···** > > On 14 août, 16:55, Simon Krahnke \ wrote: ---
**Author:** ![Gavin\_Kistner3](https://avatars.discourse-cdn.com/v4/letter/g/dfb087/32.png) [@Gavin\_Kistner3](https://rubytalk.org/u/Gavin_Kistner3)\ **Post date:** [14 August 2007 16:45 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/7 "2007-08-14T16:45:00Z")
Despite the name, sprintf does not actually print the value to stdout. I prefer its more terse version, String#%: C:\\>irb irb(main):001:0\> n = 509 =\> 509 irb(main):002:0\> s = "%04o" % n =\> "0775" For more info, "ri sprintf" or "ri String#%" > **···** > > On Aug 14, 6:56 am, unbewust \ wrote: > > > On 14 août, 11:31, Eric Hodel \ wrote: > > \> The easiest way will probably be to use sprintf. From C, use > > \> rb\_f\_sprintf. > > > OK, thanks, but i don't want to print it just have it as a return > > value then you mean i can use sprintf to print to stdout and the value > > will be cached by Ruby ? ---
**Author:** ![Eric\_Hodel1](https://avatars.discourse-cdn.com/v4/letter/e/a9adbd/32.png) [@Eric\_Hodel1](https://rubytalk.org/u/Eric_Hodel1)\ **Post date:** [14 August 2007 18:34 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/8 "2007-08-14T18:34:29Z")
sprintf returns a String. You can print it with puts if you want, or use it later. > **···** > > On Aug 14, 2007, at 05:59, unbewust wrote: > > > On 14 août, 11:31, Eric Hodel \ wrote: > > > > > On Aug 14, 2007, at 01:49, unbewust wrote: > > > > > > > i write a C extension to Ruby, some methods are dealing with octal > > > > number (bytes in english ?) for the file permission : > > > > > > > > ie something like that : > > > > > > > > 0777 or 0644 the first 0 (zero) meaning the following is a number > > > > coded in octal. > > > > > > > > that's OK for input of octal number if for example, from ruby the user > > > > write : > > > > > > > > this\_file.perms = 0777 (then with the first 0) > > > > > > > > i get the right number > > > > > > > > however, for the time being, i'm returning, for the same value : > > > > > > > > 777 instead of 0777 when the user wants to read the perms, then my > > > > question how to return within a C est to Ruby an integer coded in > > > > octal ??? > > > > > > > > thought, at that time i'm usinbg INT2FIX ( ) > > > > > > The easiest way will probably be to use sprintf. From C, use > > > rb\_f\_sprintf. > > > > OK, thanks, but i don't want to print it just have it as a return > > value then you mean i can use sprintf to print to stdout and the value > > will be cached by Ruby ? > > -- > Poor workers blame their tools. Good workers build better tools. The > best workers get their tools to do the work for them. -- Syndicate Wars ---
**Author:** ![Simon\_Krahnke](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Simon\_Krahnke](https://rubytalk.org/u/Simon_Krahnke)\ **Post date:** [15 August 2007 11:04 UTC](https://rubytalk.org/t/c-ext-to-ruby-how-to-output-a-octal-coded-number/39883/9 "2007-08-15T11:04:58Z")
\* unbewust \ (17:31) schrieb: > > num = "775".to\_i(8) > > dec = num.to\_s #\> "509" > > oct = num.to\_s(8) #\> "775" > > i've allready a way to output my number as an octal "775" BUT i'll > like having better "0775" because in the C language the first 0 means > octal and i ask for xhen input . I don't quite understand the purpose of your extension. Normally you do interaction with the user in ruby code. mfg, simon .... l