PS1 is not implemented as specified in IEEE Std 1003.1-2017

[Berthold Lorke <berthold@lorke.de>]

Hello!

The POSIX standard specifies for PS1 
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html


```
PS1

Each time an interactive shell is ready to read a command, the value of 
this variable shall be subjected to parameter expansion and written to 
standard error. The default value shall be "$ ". For users who have 
specific additional implementation-defined privileges, the default may 
be another, implementation-defined value. The shell shall replace each 
instance of the character '!' in PS1 with the history file number of the 
next command to be typed. Escaping the '!' with another '!' (that is, 
"!!" ) shall place the literal character '!' in the prompt. This volume 
of POSIX.1-2017 specifies the effects of the variable only for systems 
supporting the User Portability Utilities option.
```

Your manual pages say

```
PS1

The primary prompt string, which defaults to “$ ”, unless you are the 
superuser, in which case it defaults to “# ”.
```

I also tried it out, the exclamation mark functionality doesn't work.

Is this as intended?


Kind regards
Berthold Lorke