[TUHS] Shell Level...

[Theodore Y. Ts'o]

On Tue, Jan 21, 2020 at 01:44:07PM -0700, Grant Taylor via TUHS wrote:
> On 1/20/20 12:40 PM, Theodore Y. Ts'o wrote:
> > The normal reason why I'm starting subshells is because I need to
> > control various environment variables on an ad-hoc basis.  It might be
> > PYTHONPATH, KRB5CCNAME, GPG_AGENT_INFO, LD_LIBRARY_PATH, or some
> > combination of the above.  Back when I was regularly using Kerberos
> > root/admin bits, I had some hard-coded shell aliases to indicate
> > explicitly I was in a shell that was using my tytso/root at ATHENA.MIT.EDU
> > or tytso/admin at ATHENA.MIT.EDU kerberos tickets.
> 
> If I'm understanding you correctly, you used a sub-shell with a modified /
> task / process specific environment.  Correct?

Correct.  And I would often suspend the shell when I didn't need to
use the Kerberos administration credentials, and then go back to it
later when I did need it, and since I was often bouncing back and
forth between the sub-shell and the parent shell, having the SHLVL
displayed in the prompt for non-top-level shells was useful.

For similar reasons, my shell prompt will also display what git branch
I happen to be one.  For example:

<tytso at lambda> {/usr/projects/e2fsprogs/e2fsprogs-maint}, level 2   (debian/master)
1001% 

Says that I'm on the debian/master git branch, and "level 2" indicates
that I'm in a subshell.  (If I'm in a top level shell, no level will
be printed at all.)  The prompt also displays the hostname ("lambda"
in this case") which is super-useful to identify remote logins.

	     	 	    		  	     - Ted