Beni Cherniavsky wrote:
> Nice idea, but defining the scope of cd locality seems a bit tricky.
> E.g. currently "begin; ...; end" is equivalent to "if true; ...; end".
> So should "cd -l" also be local to "if"? To any construct delimited by "end"?
> This is not always desired - consider::
>
> begin
> if COND
> cd SOME-DIR
> else
> cd OTHER-DIR
> end
> DO-SOMETHING-IN-DIR
> end
>
> where the "cd" should not be local to the "if" but should be local to
> the "begin".
> This is just an example. I'm not sure it proves anything, but I fear
> there is no single clean and useful definition for the scope for "cd
> -l"...
use functional style. Admittedly it's a bit annoying in fish, but doable.
begin
cd -l (if COND
echo SOME-DIR
else
echo OTHER-DIR
end)
DO-SOMETHING-IN-DIR
end
or,
begin
set -l dir #define the scope... of modifications to the var
if COND
set dir SOME-DIR
else
set dir OTHER-DIR
end
cd -l $dir
DO-SOMETHING-IN-DIR
end
But that makes me think it could be the same as
begin
cd -l #define the scope... of modifications to the cwd
if COND
cd SOME-DIR
else
cd OTHER-DIR
end
DO-SOMETHING-IN-DIR
end
which is actually equivalent in usage to what you suggest here:
> Alternative proposal: a new "saved [DIR]; ...; end" construct that
> explicitly saves and restores the working directory in that block
> (temporarily changing to DIR if given).
aka just like pushd/popd but more reliable.
> Alternative 2 (half-baked): some kind of "try..finally..end" construct
> to ensure the execution of things like "popd"?
I don't like it much. I forget what kind of "exceptions" fish has.
Depends if we come up with any other examples of things that have to be
restored (and if we can also do the cleanup C++ RAII style, positioning
the cleanup in the same place in the script code as where the thing that
needs to be cleaned up is begun)
now, if only there were a good way to call back into fish from commands,
e.g.
set FOOL foo
#imaginary parenthesis syntax to create a command not a string:
env FOOL=bar (echo 3; cd $FOOL; set FOOL $FOOL)
#where does the "3" go to? Are we in the "bar" directory now?
#Does FOOL have its prior value, or "bar"?
#Fish hates the idea of subshells, remember...
sudo (cat $FOOL > /sys/wherever)
But I fear issues of variable scoping (environmental, cwd...) and pipes
(stdout,stderr...) might make that too unintuitive no matter how it's done.
(if we did, we could perhaps just make more commands that didn't have to
be part of the shell)
-Isaac
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