[t]csh prompt magic

I refer to Jan’s
smiley system. I like the idea, and tried to implement something similar
in [t]csh… with only limited success.

First of all, I needed an equivalent of that bash function inspecting the
return value of the previous command and printing a corresponding smiley.
[t]csh doesn’t support functions, so I needed an alias. But in aliases, you
can’t use if-then-else. Or so I thought.
But this works:

set echo_style = both
alias smiley 'eval "if (\$?) then \\
echo -n \\e[1m\\e[31m- $?\\e[m" " \\
else \\
echo -n \\e[1m\\e[32m+\\e[m" " \\
endif"'

Watch your quoting; remember that the shell strips off one level of quoting
when you set the alias and another during the first pass of the eval. The
echo_style could also be just ``sysv'', but not ``none'' or ``bsd'' if you
want some colour instead of a scrambled shell. And, oh yes. Smileys won't
work, as there is no way I could make this statement not
evaluate ('s or )'s correctly (unless maybe I try it with makealias or
quote one day), so I opted for the +
and - signs instead.

Now after figuring this out, I needed a way to get an alias call into my
$prompt variable. Bummer. No support for this in [t]csh. Yikes!

So now what? Well, you could just set the printexitvalue shell variable to
print the exit status of commands which exit with a status other than zero,
which is supported by default by [t]csh.

So, the same functionality can be gotten (even far simpler than in bash), but
not the same coolness factor. Too bad for those [t]csh users out there. :-)