opencontainers 0.0.0-alpha.2

user = ${ user_spec | user_spec ~ ":" ~ group_spec }

user_spec = { username | uid }
group_spec = { group | gid }

username = _{ ident }
group = _{ ident }

uid = _{ number }
gid = _{ number }

ident = _{ ASCII_ALPHA ~ (ASCII_ALPHA | ASCII_DIGIT)* }
number = _{ ASCII_DIGIT+ }