I usually call it non-interactively:

  $ units 1500DKK USD
      * 236.76653
      / 0.00422357

in which case it's always the first line I want.

(The second line is telling me 1USD is 0.00422357 of 1500DKK.)

Note if you use the currency conversions,

  systemctl enable units-currency-update.timer

is needed to keep them up-to-date.

If you only need the first line you can invoke units with --terse.

  $ units --terse 2.4kWh megajoules
  8.64

The * value is the result of converting 10 miles to meters, as requested.

The / value is the inverse of that in case you wanted that, ie 0.1 meters in miles.

It's explained in `man 1 units`

Oh, I know it's explained in the man page. I read it every time and promptly forget because I can't internalize the choice of notation.

If you find the output a bit hard to parse at times (as I do), you might want to try qalc instead, I use it all the time from the terminal to do conversions:

    $ qalc 
    > 3 millilightseconds to miles

      3 milliLightSeconds ≈ 558 mi + 1491 yd + 0.1692913386 ft

I'm not sure if it has all the same units as `units` does, but it replaced my use of it entirely as it can do other useful operations as well

* multiply

/ divide

I am familiar.

the * is denoting the conversion from your first unit to your second, the / denotes the other way.

You have: 1 miles You want: feet * 5280 / 0.00018939394

In the above example, 1 mile is 5280 feet, and 1 foot is 0.00018939394 miles

If I do 2 miles to feet, the values are doubled (or halved for the reverse conversion)

You have: 2 miles You want: feet * 10560 / 9.469697e-05