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
