Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!sun-barr!newstop!sun!amdcad!dgcad!dg-rtp!wgate!lanzo
From: lanzo@wgate.UUCP (Mark Lanzo)
Newsgroups: comp.unix.shell
Subject: Re: adjusting string var to fixed length (in ksh)
Keywords: ksh, typeset
Message-ID: <193@atesysv.UUCP>
Date: 12 Jun 91 20:54:21 GMT
References: <9106111833.AA07449@ucbvax.Berkeley.EDU>
Reply-To: lanzo@atesysv.UUCP (Mark Lanzo)
Organization: Wandel & Goltermann Technologies, Inc.
Lines: 37

"Mark" == Mark Lanzo <lanzo@atesysv.UUCP>    [that's me]
"Dan"  == Dan_Jacobson@ihlpz.ATT.COM 

From prior posts:
    Mark> If you are using "ksh" [...]
    
    Mark> 	myname=Mark
    Mark> 	typeset -L10 myname
    
Dan>    In my prompt I wanted to put $? (last command exit status) in a fixed
Dan>    width... (PS1='$? '...) but I can't typeset -L3 ? or \?...

Hmm.  As far as I know, you're out of luck with this.
You're right, "typeset" doesn't work on special parameters like "$?"; 
it just complains that "?" isn't a valid identifier.

Even if "typeset" _did_ work on $?, I think you'd still be out of luck.
Ksh evaluates PS1 and performs *parameter substitution* on the string,
but it does not perform *command substitution* on it.  (Drats!)

In other words, you can't use the `command` or $(command) forms within
PS1 in any meaningful fashion.

For example, to display the current directory in the prompt:
      PS1='$PWD> '        # Works
      PS1='`pwd`> '       # Does not work
      PS1='$(pwd)> '      # Does not work

I even tried screwier things, to see if any sort of recursive evaluation
mechanisms could be faked out, such as

      PS1='${?:+`pwd`}'

... to no avail.


If anyone else has a solution, I'd like to hear about it ...
                    -- Mark --