Session recording

[VirginSnow at vfemail.net]

> Date: Mon, 31 Mar 2008 17:59:11 -0400 (EDT)
> From: "John Abreau" <jabr at blu.org>
> Cc: gnhlug-discuss at mail.gnhlug.org

> >> ...
> >>  export PS1='[ `date` ]'
> >> ...
> >>
> >
> > Note: That will probably not do what you intended...  Each time a
> > prompt is issued, the same exact prompt will be issued, namely
> > "[ Mon Mar 31 17:32:54 UTC 2008]".  "date" will not be rerun
> > before each prompt.  To do that, you need to use $PROMPT_COMMAND.
> 
> 
> Did you try it first before declaring that it won't work?
> I just gave it a try, and it does indeed run the date
> command for each prompt.
> 
>     [ Mon Mar 31 17:54:54 EDT 2008 ]
>     [ Mon Mar 31 17:54:57 EDT 2008 ]
>     [ Mon Mar 31 17:55:04 EDT 2008 ]

I said it would "probably" not do what was intended.  I was "probably"
wrong, as well. :)

As it turns out, it REALLY depends on the value of the "promptvars"
shell option.

  user at localhost$ shopt -s promptvars
  user at localhost$ PS1='[ `date` ] $ '
  [ Mon Mar 31 19:34:51 EDT 2008 ] $ 
  [ Mon Mar 31 19:34:52 EDT 2008 ] $ 
  [ Mon Mar 31 19:34:53 EDT 2008 ] $ 
  [ Mon Mar 31 19:34:54 EDT 2008 ] $ shopt -u promptvars
  [ `date` ] $ 
  [ `date` ] $ 
  [ `date` ] $ 
  [ `date` ] $ 

I was thinking you'd have to use PS1='[ \D{%x %X} ] $ '.  But it seems
that I was wrong.  That happens on occasion. :) Using \D doesn't spawn
extra processes with each prompt, so my way is more efficient
anyway. :P (Watch, now somebody'll prove me wrong about that too..!)