# File#file\_descriptor **URL:** \ **Category:** ruby-talk\ **Created:** [11 September 2007 21:16 UTC](https://rubytalk.org/t/file-file-descriptor/40551 "2007-09-11T21:16:00Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Wayne\_E\_Seguin](https://avatars.discourse-cdn.com/v4/letter/w/d26b3c/32.png) [@Wayne\_E\_Seguin](https://rubytalk.org/u/Wayne_E_Seguin)\ **Post date:** [11 September 2007 21:16 UTC](https://rubytalk.org/t/file-file-descriptor/40551/1 "2007-09-11T21:16:00Z")
Hopefully someone knows this... I've googled for a while. When writing a C extension, how does one access the file descriptor of a File object from the C code? Thanks!    ~Wayne s///g Wayne E. Seguin Sr. Systems Architect & Systems Administrator ---
**Author:** ![Joel\_VanderWerf1](https://avatars.discourse-cdn.com/v4/letter/j/94ad74/32.png) [@Joel\_VanderWerf1](https://rubytalk.org/u/Joel_VanderWerf1)\ **Post date:** [11 September 2007 21:26 UTC](https://rubytalk.org/t/file-file-descriptor/40551/2 "2007-09-11T21:26:11Z")
Wayne E. Seguin wrote: > Hopefully someone knows this... I've googled for a while. > > When writing a C extension, how does one access the file descriptor of a File object from the C code? Take a look at this method in io.c: static VALUE rb\_io\_fileno(io)      VALUE io; {      OpenFile \*fptr;      int fd;      GetOpenFile(io, fptr);      fd = fileno(fptr-\>f);      return INT2FIX(fd); } > **···** > > -- >        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407 ---
**Author:** ![Eric\_Hodel1](https://avatars.discourse-cdn.com/v4/letter/e/a9adbd/32.png) [@Eric\_Hodel1](https://rubytalk.org/u/Eric_Hodel1)\ **Post date:** [11 September 2007 21:27 UTC](https://rubytalk.org/t/file-file-descriptor/40551/3 "2007-09-11T21:27:04Z")
$ ri IO#fileno -------------------------------------------------------------- IO#fileno       ios.fileno =\> fixnum       ios.to\_i =\> fixnum > **···** > > On Sep 11, 2007, at 14:16, Wayne E. Seguin wrote: > > > Hopefully someone knows this... I've googled for a while. > > > > When writing a C extension, how does one access the file descriptor of a File object from the C code? > > ------------------------------------------------------------------------ >       Returns an integer representing the numeric file descriptor for >       ios. > >          $stdin.fileno #=\> 0 >          $stdout.fileno #=\> 1 > >       (also known as to\_i) > > -- > 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\_Hunter4](https://avatars.discourse-cdn.com/v4/letter/t/ea5d25/32.png) [@Tim\_Hunter4](https://rubytalk.org/u/Tim_Hunter4)\ **Post date:** [11 September 2007 21:30 UTC](https://rubytalk.org/t/file-file-descriptor/40551/4 "2007-09-11T21:30:24Z")
Wayne E. Seguin wrote: > Hopefully someone knows this... I've googled for a while. > > When writing a C extension, how does one access the file descriptor of a File object from the C code? > > Thanks! > >   ~Wayne > > s///g > Wayne E. Seguin > Sr. Systems Architect & Systems Administrator Check the GetOpenFile macro in rubyio.h. > **···** > > -- > RMagick OS X Installer [[http://rubyforge.org/projects/rmagick/\](http://rubyforge.org/projects/rmagick/%5C)] > RMagick Hints & Tips [[http://rubyforge.org/forum/forum.php?forum\_id=1618\](http://rubyforge.org/forum/forum.php?forum_id=1618%5C)] > RMagick Installation FAQ [[http://rmagick.rubyforge.org/install-faq.html\](http://rmagick.rubyforge.org/install-faq.html%5C)] ---
**Author:** ![Wayne\_E\_Seguin](https://avatars.discourse-cdn.com/v4/letter/w/d26b3c/32.png) [@Wayne\_E\_Seguin](https://rubytalk.org/u/Wayne_E_Seguin)\ **Post date:** [12 September 2007 01:25 UTC](https://rubytalk.org/t/file-file-descriptor/40551/5 "2007-09-12T01:25:11Z")
Joel, Awesome, this is exactly what I was looking for! Thank you!    ~Wayne s///g Wayne E. Seguin Sr. Systems Architect & Systems Administrator > **···** > > On Sep 11, 2007, at 17:26 , Joel VanderWerf wrote: > > > Wayne E. Seguin wrote: > > > > > Hopefully someone knows this... I've googled for a while. > > > When writing a C extension, how does one access the file descriptor of a File object from the C code? > > > > Take a look at this method in io.c: > > > > static VALUE > > rb\_io\_fileno(io) > >     VALUE io; > > { > >     OpenFile \*fptr; > >     int fd; > > > >     GetOpenFile(io, fptr); > >     fd = fileno(fptr-\>f); > >     return INT2FIX(fd); > > } ---
**Author:** ![Wayne\_E\_Seguin](https://avatars.discourse-cdn.com/v4/letter/w/d26b3c/32.png) [@Wayne\_E\_Seguin](https://rubytalk.org/u/Wayne_E_Seguin)\ **Post date:** [12 September 2007 01:30 UTC](https://rubytalk.org/t/file-file-descriptor/40551/6 "2007-09-12T01:30:24Z")
Thank you Tim! Most helpful.    ~Wayne s///g Wayne E. Seguin Sr. Systems Architect & Systems Administrator > **···** > > On Sep 11, 2007, at 17:30 , Tim Hunter wrote: > > > Wayne E. Seguin wrote: > > > > > Hopefully someone knows this... I've googled for a while. > > > > > > When writing a C extension, how does one access the file descriptor of a File object from the C code? > > > > > > Thanks! > > > > > >   ~Wayne > > > > > > s///g > > > Wayne E. Seguin > > > Sr. Systems Architect & Systems Administrator > > > > Check the GetOpenFile macro in rubyio.h.