title: Raspberry PI, GPIO Pull UP/DOWN resistors with SYSFS
body: <p>Just off the bat I'd like to state that I'm aware of Python and other high level implementations for manipulating GPIO on the Raspberry PI. I've also been using the WiringPI C API and am experiencing problems with it on Raspbian Jessie that I was not having on Raspbian Wheezy even though I have not changed a single line of code. Also the WiringPI C API developer says he has no immediate plans to support Raspbian Jessie so I'm kind of up a creek without a paddle.</p>
  
  <p>For this reason I've been reading the following tutorial (among others) on accessing Raspberry PI GPIOs using <strong>sysfs</strong> since this seems to be one way of addressing GPIO without using WiringPI and without writing my own GPIO library:</p>
  
  <p><a href="http://www.hertaville.com/introduction-to-accessing-the-raspberry-pis-gpio-in-c.html" rel="noreferrer">http://www.hertaville.com/introduction-to-accessing-the-raspberry-pis-gpio-in-c.html</a></p>
  
  <p>According to this tutorial, to set GPIO17 as an input, you write the string <strong>'in'</strong> to the file handle:</p>
  
  <p><strong>/sys/class/gpio/gpio/17/direction</strong></p>
  
  <p>...and then I can read GPIO input values from:</p>
  
  <p><strong>/sys/class/gpio/gpio17/value</strong></p>
  
  <p>This is all well and good but I do not have the option of retro fitting pull-up resistors to my production boards. Is it possible to set the Raspberry PI's built in pull-up and pull-down resistors using <strong>sysfs</strong>?</p>
  
  <p>Also, if setting the pull-up and pull-down resistors via <strong>sysfs</strong> is not possible am I correct in assuming that even in the latest Raspbian Jessie the only other way to do this is write directly to GPIO registers? i.e. even in Raspbian Jessie there is no official C API for GPIO programming?</p>