ubuntu - 为什么 setuid 不作为所有者运行？

Question

我目前正在尝试了解文件权限中的特殊位的作用，但目前正试图了解 setuid 位的作用。从所有在线资源中，它说:

Commonly noted as SUID, the special permission for the user access level has a single function: A file with SUID always executes as the user who owns the file, regardless of the user passing the command

然而，在一个简单的实验中，这似乎并不正确(除非我误解并且做错了什么？)即

mkdir /tmp/foo
mkdir /tmp/foo/bar
chmod 0700 /tmp/foo/bar                        # Restrict directory so only current user can access
echo content > /tmp/foo/bar/baz.txt            # Create content in the restricted directory
echo "ls /tmp/foo/bar" > /tmp/foo/myscript.sh  # Script to access content of restricted directoy
chmod 4777 /tmp/foo/myscript.sh                # Set setuid bit so the script runs as current user
/tmp/foo/myscript.sh                           # Show it works when run as current user

#> baz.txt

su bob                 # Switch to a new user
/tmp/foo/myscript.sh   # Run script again

#> ls: cannot open directory '/tmp/foo/bar': Permission denied

我的期望是，由于设置了 setuid 位，脚本应该以原始用户身份执行，因此应该拥有 ls 的权限。进入受限目录。但相反，我收到了一个权限被拒绝的错误，表明该脚本没有以原始用户身份运行。
任何帮助理解我做错了什么都将不胜感激。 (示例在 zsh/ubuntu 20.04/wsl2 上运行)

Answer 1

suid 位仅适用于二进制可执行程序，不适用于 shell 脚本。您可以在这里找到更多信息:https://unix.stackexchange.com/questions/364/allow-setuid-on-shell-scripts