/usr/share/ri/1.8/system/Bignum/ is in ri1.8 1.8.7.352-2ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/ri/1.8/system/Bignum/%25-i.yaml
/usr/share/ri/1.8/system/Bignum/%26-i.yaml
/usr/share/ri/1.8/system/Bignum/%2a%2a-i.yaml
/usr/share/ri/1.8/system/Bignum/%2a-i.yaml
/usr/share/ri/1.8/system/Bignum/%2b-i.yaml
/usr/share/ri/1.8/system/Bignum/%2d%40-i.yaml
/usr/share/ri/1.8/system/Bignum/%2d-i.yaml
/usr/share/ri/1.8/system/Bignum/%2f-i.yaml
/usr/share/ri/1.8/system/Bignum/%3c%3c-i.yaml
/usr/share/ri/1.8/system/Bignum/%3c%3d%3e-i.yaml
/usr/share/ri/1.8/system/Bignum/%3d%3d-i.yaml
/usr/share/ri/1.8/system/Bignum/%3e%3e-i.yaml
/usr/share/ri/1.8/system/Bignum/%5b%5d-i.yaml
/usr/share/ri/1.8/system/Bignum/%5e-i.yaml
/usr/share/ri/1.8/system/Bignum/%7c-i.yaml
/usr/share/ri/1.8/system/Bignum/%7e-i.yaml
/usr/share/ri/1.8/system/Bignum/abs-i.yaml
/usr/share/ri/1.8/system/Bignum/cdesc-Bignum.yaml
/usr/share/ri/1.8/system/Bignum/coerce-i.yaml
/usr/share/ri/1.8/system/Bignum/div-i.yaml
/usr/share/ri/1.8/system/Bignum/divmod-i.yaml
/usr/share/ri/1.8/system/Bignum/eql%3f-i.yaml
/usr/share/ri/1.8/system/Bignum/fdiv-i.yaml
/usr/share/ri/1.8/system/Bignum/hash-i.yaml
/usr/share/ri/1.8/system/Bignum/modulo-i.yaml
/usr/share/ri/1.8/system/Bignum/power%21-i.yaml
/usr/share/ri/1.8/system/Bignum/quo-i.yaml
/usr/share/ri/1.8/system/Bignum/rdiv-i.yaml
/usr/share/ri/1.8/system/Bignum/remainder-i.yaml
/usr/share/ri/1.8/system/Bignum/rpower-i.yaml
/usr/share/ri/1.8/system/Bignum/size-i.yaml
/usr/share/ri/1.8/system/Bignum/to_f-i.yaml
/usr/share/ri/1.8/system/Bignum/to_s-i.yaml