How do I extract variables from a list in fish?

Question

So, I recently downloaded a cli which shares a lot of commands similar to linux. Like mega-login : login & mega-logout :logout and I am too tired of writing mega every time I need to use the cli. I thought of using alias but I don't want to screw some other program that use the some other command I don't know of. Like if I create an alias login then what will happen to the system login command? Plus there are a lot of commands in the cli.

So, I thought of using a script, but I didn't know how to do it. Here what I had in my mind. So when I use m login or m logout it will search if a command mega-login or mega-logout exists and then call it.

So I tried hours coming up with various functions while learning fish and this is what I wrote.

function m --argument value $argv
    echo value $value $argv
    if type mega-$value
        set MEGA
        for temp in $argv
            set MEGA $MEGA$temp
            echo $MEGA
        end
        echo MEGA \n\n $MEGA
        eval $MEGA
    end
end

This still doesn't work. PS: I wrote this on my first try, but I dropped it once I couldn't figure it out.

function m --argument value $argv
    echo value $value $argv
    if type mega-$value
        set MEGA mega-$argv
        echo $argv \n\n\n $MEGA
    eval $MEGA
    end
end

Answer 1

Not a bad first (and second) attempt. It can be tricky to get it just right.

How about:

function m
    set -l mega_cmd "mega-$argv[1]"
    set -l mega_args $argv[2..]
    if type -q "$mega_cmd"
        echo "Executing $mega_cmd $mega_args"
        "$mega_cmd" $mega_args
    end
end

Of course, that's for readability (which I prefer), but it can be condensed down to:

function m
    if type -q "mega-$argv[1]"
        echo "Executing mega-$argv[1] $argv[2..]"
        "mega-$argv[1]" $argv[2..]
    end
end