Support commandline local variables

[creack]

It would be nice to have the ability to set a temporary environment variable.

Right now, in order to do this, I have to write;
set -x VAR value; cmd; set -e VAR.

In any other shell, you can do this:
VAR=value cmd

Fish is not any other shell, I know.. But I don't think it is a reason to strip must have features like this ;)

[zanchey]

See also #438, #587, #809, #823...

[creack]

@zanchey What is the official position on this? If I sum-up the threads:

$> fish -v
fish, version 2.1.0

$> env VAR=world echo hello $VAR
hello

$> env VAR=world; echo hello $VAR
#...
#displays my whole env
hello

$> begin; set -lx VAR world; echo hello $VAR; end
hello world

$> function myfct; echo hello $VAR; end
$> begin; set -lx VAR world; myfct; end
hello

$> set -lx VAR world; echo hello $VAR
hello world
#leaks the var (expected I think)

[ridiculousfish]

env is an external command, so it can't do things like modify the value of a variable before it gets expanded. This is one of many reasons why it's an imperfect substitute for the foo=bar syntax in POSIX shells.

This is obviously a very popular request, but the foo=bar syntax is not in line with fish's "everything is a command" design principle. So how can we satisfy these use cases in a way that's consistent with what makes fish fish? That's the question to think about.

If you agree this is the same as #438, I'd like to close as a dup of that.

[creack]

I agree, but 1) the solution proposed does not work (and the faq neither) 2) I am sure we can find an easy way to work around this. What about an extra flag to set? Like set -l but scoped to the commandline instead of the function

[maxfl]

Here is the right way:

set var hello
function fcn -S
    echo $var
end
begin
    set -l var world
    echo $var
    fcn
end

By default function doesn't see outer scope local variables.

[ridiculousfish]

Let's track in #438