[lug] Subshell behavior with potato bash?

[socket at peakpeak.com]

Tkil <tkil at scrye.com> writes:
> Chris> f="$(who | grep $(tty | sed s./dev/..))"
> 
> hm.  what are you trying to use this for?  it doesn't seem too much
> more informative than just "tty" by itself.  further, "last -1" might
> be more what you're looking for.  or actually:
> 
>    last -1 `id -un`
> 
> maybe.
> 
> then again, i don't know what you're trying to do.  :)

Well, the *full* story behind this is that I decided I wanted to learn
something real about shells last summer from a friend of mine, Aaron,
who is actually on this list and who posted yesterday with a fix for
me.  The line in question is part of a block of code used to set and
export a REMOTEHOST variable.  Unless he got it from somewhere else,
I'm assuming he wrote this block, and I haven't changed it at all,
except (as I read it now, in fact) to specify a usable case for the
domain.  At least, that's how I'm reading it so far.

With the fix he gave me yesterday, it looks something like this:

f=($tty); f="$(who | grep "${f#/dev/}")"

if echo "$f" | grep -q "("; then
        REMOTEHOST="$(echo "$f" | sed 's/^.*(\([a-zA-Z0-9_.-]*\)).*$/\1/')"
        case "$REMOTEHOST" in
        *.colorado.*)
                REMOTEHOST="$(echo "$REMOTEHOST" | sed 's/^\([^.]*\)[.]colorado[.].*$/\1/')"
		export REMOTEHOST
                ;;
        esac
        export REMOTEHOST
fi

I changed the case from a specific *.domain.* that Aaron was once
associated with to *.colorado.*, (though in my case, it would make
more sense to do *.colorado.edu, once I figure out just how to avoid
breaking that sed bit, since the university isn't likely to change
away from .edu, so I would definitely want to make sure I'm working
within colorado.edu when I need to know about REMOTEHOST...)

I suppose it's useful occasionally for things like this to break
occasionally, to remind me of my goal to learn about shells.  It's
about time I went through some of this stuff.

Thanks.

--
Chris Riddoch                  socket at peakpeak.com
Will provide pseudo-insightful commentary for food
                   http://www.peakpeak.com/~socket

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