/usr/share/acl2-7.1/books/std/io/ is in acl2-books 7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-7.1/books/std/io/base.o
/usr/share/acl2-7.1/books/std/io/combine.o
/usr/share/acl2-7.1/books/std/io/file-measure.o
/usr/share/acl2-7.1/books/std/io/nthcdr-bytes.o
/usr/share/acl2-7.1/books/std/io/print-objects.o
/usr/share/acl2-7.1/books/std/io/read-file-bytes.o
/usr/share/acl2-7.1/books/std/io/read-file-characters-no-error.o
/usr/share/acl2-7.1/books/std/io/read-file-characters.o
/usr/share/acl2-7.1/books/std/io/read-file-lines.o
/usr/share/acl2-7.1/books/std/io/read-file-objects.o
/usr/share/acl2-7.1/books/std/io/read-ints.o
/usr/share/acl2-7.1/books/std/io/read-string-raw.o
/usr/share/acl2-7.1/books/std/io/read-string-tests.o
/usr/share/acl2-7.1/books/std/io/read-string.o
/usr/share/acl2-7.1/books/std/io/serialize-tests.o
/usr/share/acl2-7.1/books/std/io/serialize-tests2.o
/usr/share/acl2-7.1/books/std/io/take-bytes.o
/usr/share/acl2-7.1/books/std/io/top.o
/usr/share/acl2-7.1/books/std/io/unsound-read-raw.o
/usr/share/acl2-7.1/books/std/io/unsound-read.o