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ARexx script to convert a value of one currency type to another.

Run from the Amiga CLI with the currency value to be exchanged
followed by the original and destination 3-letter currency codes.

Currency conversion data provided by
https://www.exchangerate-api.com

Conversion detail for the base currency type to all other
currencies is automatically cached in T: for 24 hours for faster
subsequent conversions.

Requires an Amiga compatible system running a TCP/IP stack,
e.g. Miami, AmiTCP, Genesis, Roadshow.

Created with and tested on A4000T/68060 AmigaOS3.2 and MiamiDX.

Both an ARexx script and a Rexecute compiled version of the script
for 68k AmigaOS is provided.  This 68k executable reportedly causes
a GrimReaper on OS4.x.  The ARexx script operates correctly on
OS4.x and should work on other Amiga-like systems with full ARexx
support, though this is untested.


Command line usage for Convert:
Convert "<Amount> <From> <To>"
e.g. Convert "1 AUD USD"


Command line usage for Convert.rexx:
rx Convert.rexx <Amount> <From> <To>
e.g. rx Convert.rexx 1 AUD USD


The compiled version of Convert requires quotation marks around the
arguments, which is something to do with Rexecute.  Floating point
numbers are accepted.
e.g.
rx Convert.rexx 1.75 AUD USD
or
Convert "1.75 AUD USD"

1.75 AUD = 1.0876600 USD


See https://www.exchangerate-api.com/docs/supported-currencies
for a full list of supported currency codes.


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History:
v0.6 2002 Michael Trebilcock
    Final Aminet release of Convert using xe.com.

v0.7 24/4/2010 Anthony Hoffman
    Re-wrote script to source currency conversion from finance.yahoo.com.

v0.8 1/2/2014 Anthony Hoffman
    The Host: header field is now sent in the server request due to a
    change on the finance.yahoo.com server which resulted in a return
    of error 404 unless the Host: header field is sent as specified
    in RFC2616-sec5.

    An invalid currency type of UKP is now converted to GBP.

v0.9 12/11/2017 Anthony Hoffman
    The finance.yahoo.com API was discontinued on 6th November 2017,
    changed script to use the free.currencyconverterapi.com API instead.

v1.0 27/2/2019 Anthony Hoffman
    From February 2019, free.currencyconverterapi.com now
    requires a free personal key to access the API.

v2.0 5/1/2025 Anthony Hoffman
    As free.currencyconverterapi.com is becoming unreliable [the site
    maintainer advises that the paid version should be used for
    reliability], moved currency conversion to exchangerate-api.com
    which has advantages of not requiring a personal API key and
    doesn't require HTTPS.

    Added automatic caching of conversion values per base currency code,
    cached data automatically refreshes once daily as needed.

    Improved validation of input arguments.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO METHOD CRC     STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[Amiga]                   9319   17076  54.6% -lh5- 49e4 Jan  6 08:58 Convert/Convert
[Amiga]                   1437    3249  44.2% -lh5- 442f Jan  6 09:50 Convert/Convert.readme
[Amiga]                   2291    6855  33.4% -lh5- 5ffa Jan  6 09:41 Convert/Convert.rexx
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         3 files   13047   27180  48.0%            Jan  6 20:35