[wuster]

Best part of reading this is coming away having learned the existence of units the CLI. How did I spend 20 years on the shell and not have needed or discovered this?

[cranium]

One thing I got bitten by was the handling of Fahrenheit/Celsius, because it's a non-linear conversion between the two. When you ask to convert `10 degC` to `degF` you get 18, which is the delta of ºF corresponding to increment of 10ºC. To get the absolute temperature, you have to ask to convert `tempC(10)` to `tempF` which is 50, as expected.

https://www.gnu.org/software/units/

[comicjk]

"Non-linear" threw me off for a second - I almost never see the mathematically correct definition of linear in computer science spaces. For anyone wondering, Celsius to Fahrenheit is an affine transform, technically not linear, because you have to add an offset, not just multiply.

[m000]

FWIW, units on macOS (not GNU) handles conversion of `10 degC` to `degF` correctly, although it dates back to 1993.

It seems that GNU units at some point added support for several non-linear units, which may have prompted them to rethink their syntax.

[ornornor]

Be aware that currencies are stuck with rates from several years ago and don’t update.

[duckerude]

Running `sudo units_cur` does the trick for me.

  $ units
  Currency exchange rates from FloatRates (USD base) on 2020-05-12
  $ sudo units_cur
  $ units
  Currency exchange rates from FloatRates (USD base) on 2020-07-09

(GNU units, packed by Debian)

[throwaway744678]

Looking at the source of the default configuration (cat /usr/share/misc/units.lib), I believe it only defines conversions for currencies that are pegged to another one (mainly to EUR or USD).

    You have: 10 franc
    You want: dollar
    conformability error
     1.5244902 euro
     1 usdollar
    You have: 10 franc
    You want: euro
     * 1.5244902
     / 0.655957

[zerocrates]

I'm tempted to say it shouldn't even attempt to support currency conversion, as constantly in flux as it is.

[gerdesj]

  $ units
  Currency exchange rates from FloatRates (USD base) on 2019-06-05

[divbzero]

I wonder if this could be addressed with periodic updates.

[lozf]

I also discovered `units` because of this tale... but I was lucky enough to read it beck in the early days (pre 2005 at least).

[pedrow]

'units' was new to me too. The version I have on my Mac wouldn't accept 'millilightseconds' but it would take 'milli-c-seconds' - presumably the units.lib database is a little different from one in the original article.

[petercooper]

Though sadly millilightseconds is not supported on macOS, at least, so you have to go:

    3 millilightyears / 365 / 86400

Of course, round 365 to whatever average number of days you believe in :-)

[punnerud]

units

You have: mph

You want: kph

        * 1.609344

        / 0.62137119

[majewsky]

I have

  alias units='units --verbose

in my shell rc which makes the output much more understandable:

  You have: mph
  You want: kph
          mph = 1.609344 kph
          mph = (1 / 0.62137119) kph

[nrzd]

Me too! so awesome