yangw@codecompile:~/RK3288_Lakala/kernel/arch/arm/boot/dts$ cd -
  /home/yangw
  yangw@codecompile:~$ pwd
  /home/yangw
  yangw@codecompile:~$ cd - 
  /home/yangw/RK3288_Lakala/kernel/arch/arm/boot/dts
  yangw@codecompile:~/RK3288_Lakala/kernel/arch/arm/boot/dts$ pwd
  /home/yangw/RK3288_Lakala/kernel/arch/arm/boot/dts
  yangw@codecompile:~/RK3288_Lakala/kernel/arch/arm/boot/dts$ cd ~
  yangw@codecompile:~$ pwd
  /home/yangw
  yangw@codecompile:~$ cd /
  yangw@codecompile:/$ pwd
  /
  yangw@codecompile:/$ cd -
  /home/yangw