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The units program database includes currency exchange rates and prices
for some precious metals. Of course, these values change over time,
sometimes very rapidly, and units
cannot provide real-time
values. To update the exchange rates, run units_cur
, which
rewrites the file containing the currency rates, typically
/var/lib/units/currency.units or
/usr/local/com/units/currency.units
on a Unix-like system or
C:\Program Files (x86)\GNU\units\definitions.units on a Windows
system.
This program requires Python 3 (https://www.python.org). The program must be run with suitable permissions to write the file. To keep the rates updated automatically, run it using a cron job on a Unix-like system, or a similar scheduling program on a different system.
Reliable free sources of currency exchange rates have been annoyingly ephemeral. The program currently supports several sources:
The default source is FloatRates; you can select a different one using -s option described below.
Precious metals pricing is obtained from Packetizer (www.packetizer.com). This site updates once per day.
The units
program includes the US Consumer Price Index (CPI)
published by the US Bureau of Labor Statistics: specifically, the
Consumer Price Index for All Urban Consumers (CPI-U), not seasonally
adjusted—Series CUUR0000SA0. The units_cur
command updates
the CPI and saves the result in cpi.units in the same location as
currency.units. The data are obtained via the BLS Public Data
API (https://www.bls.gov/developers/). These data update once a
month. When units_cur
runs it will only attempt to update the
CPI data if the current CPI data file is from a previous month, or if
the current date is after the 18th of the month.
units_cur
You invoke units_cur
like this:
units_cur [options] [currency_file] [cpi_file]
By default, the output is written to the default currency and CPI files
described above; this is usually what you want, because this is where
units
looks for the files. If you wish, you can specify
different filenames on the command line and units_cur
will
write the data to those files. If you give ‘-’ for a file it will
write to standard output.
The following options are available:
-h
--help
Print a summary of the options for units_cur
.
-V
--version
Print the units_cur
version number.
-v
--verbose
Give slightly more verbose output when attempting to update currency exchange rates.
-s source
--source source
Specify the source for currency exchange rates; currently supported values are ‘floatrates’ (for FloatRates), ‘eubank’ (for the European Central Bank), ‘fixer’ (for Fixer), and ‘openexchangerates’ (for open exchange rates); the last two require an API key to be given with the -k option.
-b base
--base base
Set the base currency (when allowed by the site providing the data).
base should be a 3-letter ISO currency code, e.g., ‘USD’.
The specified currency will be the primitive currency unit used by
units
. You may find it convenient to specify your local
currency. Conversions may be more accurate and you will be able to
convert to your currency by simply hitting Enter at the
‘You want:’ prompt. This option is ignored if the source
does not allow specifying the base currency. (Currently only
floatrates supports this option.)
-k key
--key key
Set the API key to key for currency sources that require it.
--blskey BLSkey
Set the US Bureau of Labor Statistics (BLS) key for fetching CPI data. Without a BLS key you should be able to fetch the CPI data exactly one time per day. If you want to use a key you must request a personal key from BLS.
Next: Database Command Syntax, Previous: Readline Support, Up: Units Conversion [Contents][Index]