How to get the size of the loop-device?

[Markus Laire <malaire@xxxxxxxxx>]

Once I have a working loop device, e.g. /dev/loop5, how can I get the
size of this device in bytes for bash-script?
I need this, so that I can create two loop-devices on top on it, like
  losetup -o 0 -s $halfsize /dev/loop6 /dev/loop5
  losetup -o $halfsize /dev/loop7 /dev/loop5

I tried trivial `perl -e 'print -s "/dev/loop5"'`, but it just returns zero.

There's likely a trivial answer to this, but I havn't been able to find it.
--
Markus Laire

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Linux-crypto:  cryptography in and on the Linux system
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