I am also struggling with the same problem. It seems that different manufacturer have different path for USB.
Mostly the real path for a usb drive is under /mnt/media_rw/ ( e.g. /mnt/media_rw/usbotg), and link path is under /storage/ (for example /storage/usbotg). However, this doesn't happen always. I have tested in 3 different brands and find out the followings:
- Lenovo Tab2 A10-30 has /storage/usbotg as the link to the USB
storage.
- Nexus 9 shows nothing for usb-relevant path.
- Samsung mobiles normally name the path /storage/UsbDiskA,
/storage/UsbDiskB, ... /storage/UsbDiskF.
When you use ADB shell command "cat /proc/mounts", you can find that some difference can be made after you plug in the USB disk. In my Lenovo tablet, it adds these two new lines:
/dev/block/vold/8:1 /mnt/media_rw/usbotg vfat
rw,dirsync,nosuid,nodev,noexec,relatime,uid=1023,gid=1023,fmask=0007,dmask=0007,allow_utime=0020,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro
0 0 /dev/fuse /storage/usbotg fuse
rw,nosuid,nodev,noexec,relatime,user_id=1023,group_id=1023,default_permissions,allow_other
0 0