This is an old revision of the document!
Your command is wrong. You ran echo as root, but are wriitng to the sysfs file as you (presumably a non-root user). File redirection is handled by the shell, and so you probably want to do: $ echo 4 | sudo tee /sys/class/gpio/exportThis will run tee, which will both output to stdout and to the passed in file; since it's being run as root, it'll write to the sysfs file as root.Hope this helps :)
