5 ms·

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

by wuster 6y ago

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?

nrzd 6y ago
Me too! so awesome
ornornor 6y ago
Be aware that currencies are stuck with rates from several years ago and don’t update.
- divbzero 6y ago
  I wonder if this could be addressed with periodic updates.
  - ornornor 6y ago
    I didn’t look too deep into it, my understanding was that the source it uses to update itself has been taken offline. There are workarounds involving data massaging and a cron but honestly that’s a lot more work than typing “1000 chf to usd” into ddg and getting the converted amount. But if you know something I don’t, maybe you could share for everyone’s benefit?
- throwaway744678 6y ago
  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 6y ago
  I'm tempted to say it shouldn't even attempt to support currency conversion, as constantly in flux as it is.
- gerdesj 6y ago
  $ units Currency exchange rates from FloatRates (USD base) on 2019-06-05
- duckerude 6y ago
  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)
  - throwaway8941 6y ago
    In case anyone else needs this: # systemctl edit units-currency-update.service [Unit] Description=Update units(1) currency rates [Service] Type=oneshot Nice=19 ExecStart=/usr/bin/units_cur # systemctl edit units-currency-update.timer [Unit] Description=Update units(1) currency rates [Timer] OnCalendar=daily AccuracySec=3h Persistent=true [Install] WantedBy=timers.target # systemctl daemon-reload # systemctl enable units-currency-update.timer
punnerud 6y ago
units You have: mph You want: kph * 1.609344 / 0.62137119
- majewsky 6y ago
  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
  - xigoi 6y ago
    I find the reciprocal thing useless, so I have units='units --compact --one-line', which gives just the number you want.
cranium 6y ago
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/ https://www.gnu.org/software/units/
- comicjk 6y ago
  "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.
  - tzs 6y ago
    On the other hand, an equation of the form y = a x + b is a linear equation. If you have Celsius and want Fahrenheit you accomplish that by applying a linear equation (F = 1.8 C + 32), so I certainly can't fault people for saying that the transformation they are doing is linear. I wonder what people would say for something using an equation of the form y = a x^2 + b x + c to transform something? I can't say that I've heard anyone talk of quadratic transformations. On the other hand, I can't think of ever transforming anything with a quadratic equation, so never had the need t speak of it. (Also, he called it a linear conversion, not a linear transformation).
- m000 6y ago
  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.
pedrow 6y ago
'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.
lozf 6y ago
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).
petercooper 6y ago
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 :-)

by wuster 6y ago

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?

nrzd 6y ago

Me too! so awesome

ornornor 6y ago

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

divbzero 6y ago
I wonder if this could be addressed with periodic updates.
- ornornor 6y ago
  I didn’t look too deep into it, my understanding was that the source it uses to update itself has been taken offline. There are workarounds involving data massaging and a cron but honestly that’s a lot more work than typing “1000 chf to usd” into ddg and getting the converted amount. But if you know something I don’t, maybe you could share for everyone’s benefit?
throwaway744678 6y ago
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 6y ago
I'm tempted to say it shouldn't even attempt to support currency conversion, as constantly in flux as it is.
gerdesj 6y ago
$ units Currency exchange rates from FloatRates (USD base) on 2019-06-05
duckerude 6y ago
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)
- throwaway8941 6y ago
  In case anyone else needs this: # systemctl edit units-currency-update.service [Unit] Description=Update units(1) currency rates [Service] Type=oneshot Nice=19 ExecStart=/usr/bin/units_cur # systemctl edit units-currency-update.timer [Unit] Description=Update units(1) currency rates [Timer] OnCalendar=daily AccuracySec=3h Persistent=true [Install] WantedBy=timers.target # systemctl daemon-reload # systemctl enable units-currency-update.timer

punnerud 6y ago

units You have: mph You want: kph * 1.609344 / 0.62137119

majewsky 6y ago
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
- xigoi 6y ago
  I find the reciprocal thing useless, so I have units='units --compact --one-line', which gives just the number you want.

cranium 6y ago

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

comicjk 6y ago
"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.
- tzs 6y ago
  On the other hand, an equation of the form y = a x + b is a linear equation. If you have Celsius and want Fahrenheit you accomplish that by applying a linear equation (F = 1.8 C + 32), so I certainly can't fault people for saying that the transformation they are doing is linear. I wonder what people would say for something using an equation of the form y = a x^2 + b x + c to transform something? I can't say that I've heard anyone talk of quadratic transformations. On the other hand, I can't think of ever transforming anything with a quadratic equation, so never had the need t speak of it. (Also, he called it a linear conversion, not a linear transformation).
m000 6y ago
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.

pedrow 6y ago

'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.

lozf 6y ago

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).

petercooper 6y ago

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 :-)