[TUHS] What's In a Prompt String?

[Steffen Nurpmeso via TUHS]

Steve Nickolas via TUHS wrote in
 <alpine.DEB.2.21.2604281508510.3328 at sd-159945.dedibox.fr>:
 |On Tue, 28 Apr 2026, segaloco via TUHS wrote:
 |
 |> UNIX has had several ubiquitous PS1s: @, %, $ and then a PS2 of >, with 
 |> these values also being configurable.  I've seen in various BTL media 
 |> folks using a . (period) or occasionally a $ but with no space between 
 |> the prompt and the command.  I've always assumed the former was 
 |> influenced by DEC and the latter by IBSYS control cards (e.x. $JOB, 
 |> $EXECUTE, etc. pre-JCL stuff).
 |>
 |> Is there any history on the rationale for default PS1 selections between 
 |> various shells?  Worth noting that % seems to be the most commonly 
 |> implemented but $ is what more people are familiar with due to the 
 |> adoption of the Bourne shell by V7 and subsequently various standards. 
 |> I mention the % as more common as it seems to be default in a greater 
 |> number of shells despite Bourne family generally having more uptake 
 |> (afaik).
 |>
 |> Did these choices of symbols have any particular significance?  I can't 
 |> recall where I read it but I heard suggested the original UNIX shell 
 |> used '@' as a prompt as it looks like a snail shell.  Can't verify this, 
 |> nor do any stories of the other symbols come to mind.  I've found the 
 |> ubiquity of PS2 '>' in graphical icons for terminal emulators odd. 
 |> That's not a super common prompt to see on UNIX compared with the 
 |> others, I find it strange that is often the prompt character chosen for 
 |> icons, implying users are often sitting at a PS2 prompt?
 |>
 |> - Matt G.
 |>
 |
 |At one point tcsh's default prompt was "> ".
 |
 |Also CP/M and MS-DOS's "A>" could be an influence, and some BASIC 
 |interpreters had ">" prompts?

Regarding shells Sven Mascheck is a good address to look at [1],
generally speaking.  He says v7 shell came with PS2 functionality,
and links a manual that says

	  PS1  Primary prompt string, by default `$ '.
[for UID 0 that was "# " instead]
	  PS2  Secondary prompt	string,	by default `> '.

Actually only V1 had

  at:
          <@ >

anything C language like was like

        promp = "% ";
        if(((uid = getuid())&0377) == 0) {
                promp = "# ";

from V4 on (and i think no shell sources of V2 and V3).

  [1] https://www.in-ulm.de/~mascheck/bourne/index.html#svr2

POSIX then standardized what was in v7, that much is plain.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)