Is there a way to prepend a command with a variable assignment like in bash?

Question

In bash one can write

CFLAGS="-O2" rvm install 2.0.0

to run rvm with that specific CFLAGS . Is there anyway to do the same in fish shell?

I know about set -x but that is not exactly the same as the environment variable will be set for the whole session instead of just for that command.

Answer 1

According to the fish FAQ, either use:

env CFLAGS="-O2" rvm install 2.0.0

(which will not work for fish builtins or functions, only external commands), or

begin
    set -lx CFLAGS="-O2"
    rvm install 2.0.0
end

(which is a little clunky; there are proposals for improvement on GitHub issue #438).

Answer 2

You can use the env command for this:

env FOO=BAR command

Will run command with env variable FOO set to BAR.