How to control GPIO pin by sysfs ?

http://www.avrfreaks.net/wiki/index.php/Documentation:Linux/GPIO#Interfaces_explained

for examples:
1. set GPIO27 direction to "output" and set value to "high"
# echo "high" > /sys/devices/virtual/gpio/gpio27/direction
# cat /sys/devices/virtual/gpio/gpio27/direction
out

# cat /sys/devices/virtual/gpio/gpio27/value
1

# echo 0 > /sys/devices/virtual/gpio/gpio27/value
# cat /sys/devices/virtual/gpio/gpio27/value
0

2. set GPIO27 to input
# echo "in" > /sys/devices/virtual/gpio/gpio27/direction
# cat /sys/devices/virtual/gpio/gpio27/direction
in