How to compare file permissions between two files?

Question

I'm trying to script a check to make sure two files have the same permissions. There are several ways to think about permissions, the most basic being a hex value (e.g. 777). How can I compare the permissions on two different regular files in bash?

touch a b
chmod 777 a
# What can I use to get the `777` value property from `a`?
if a.perms == b.perms; then
  echo "File permissions match!"
fi

Answer 1

stat, with the right options, seems to provide a way to compare this property, but not to an arbitrary permissions argument (e.g. 777 or +x). For that you'll want to choose the appropriate representation (e.g. %A or %a). See more in the man page.

$ echo "$(stat -c '%a' a)"
777

perms_a="$(stat -c '%a' a)"
perms_b="$(stat -c '%a' b)"
if [ ${perms_a} = ${perms_b} ]; then
  echo "Permissions match!"
else
  echo "NO match."
fi