linux下shadow 是啥

sudo chmod 640 /etc/shadow
sudo chown root:shadow /etc/shadow

sudo passwd -e username  # 强制用户更改密码

sudo cat /etc/shadow  # 使用超级用户权限查看

import crypt
import datetime
import pwd
import spwd

def check_password_expiration(username):
    try:
        shadow_entry = spwd.getspnam(username)
        expiration_date = datetime.datetime.fromtimestamp(int(shadow_entry.sp_lstchg))
        current_date = datetime.datetime.now()
        days_until_expiration = (expiration_date - current_date).days
        
        if days_until_expiration <= 7:
            print(f"Warning: {username}'s password will expire in {days_until_expiration} days.")
        else:
            print(f"{username}'s password is valid for another {days_until_expiration} days.")
    except KeyError:
        print(f"User {username} not found.")

check_password_expiration('exampleuser')