$ strace mkdir -pm2750 foo ... mkdir("foo", 02750) = 0 open("foo", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_DIRECTORY|O_NOFOLLOW) = 3 fstat(3, {st_mode=S_IFDIR|0750, st_size=4096, ...}) = 0 fchmod(3, 02750) = 0 <--- ...