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I recommend the "-1" (also called "--one-line") flag for bc.

It takes away the extra (to me) reciprocal conversion factors. (Note: it's the number one, not a lowercase "L".)

Without:

    $ units 
    Currency exchange rates from FloatRates (USD base) on 2019-05-31 
    3460 units, 109 prefixes, 109 nonlinear units
    
    You have: inch
    You want: cm
     * 2.54
     / 0.39370079
    You have: 
With:

    $ units -1
    Currency exchange rates from FloatRates (USD base) on 2019-05-31 
    3460 units, 109 prefixes, 109 nonlinear units
    
    You have: inch
    You want: cm
     * 2.54
    You have: 
To me the reciprocals are just clutter. If I want a reciprocal, I will just type the two parts of my query in the opposite order. I'd even say they're confusing because you have to look at them understand why there are two numbers.

(Also on the subject of flags, I'd like one that suppresses the first two lines of output but not the prompts like "You have:".)



Did you paste that printout from a recent run of units? If so, the currency rates are pretty useless. You can configure the system to update them daily (or however you like) with something like this:

  $ cat /etc/systemd/system/units-currency-update.service
  [Unit]
  Description=Update units(1) currency rates
  
  [Service]
  Type=oneshot
  Nice=19
  
  ExecStart=/usr/bin/units_cur
  
  
  
  $ cat /etc/systemd/system/units-currency-update.timer
  [Unit]
  Description=Update units(1) currency rates
  
  [Timer]
  OnCalendar=daily
  AccuracySec=3h
  RandomizedDelaySec=3h
  Persistent=true
  
  [Install]
  WantedBy=timers.target
  
  
  # systemctl daemon-reload
  # systemctl enable units-currency-update.timer


Or just something like

  0 0 * * * nice -n 19 /usr/bin/units_cur
for *BSD crontabs or both HN users (besides me) who prefer systemd-free distros of GNU


Corrections (b/c too late to edit):

(1) The flag isn't for bc, of course; it's for units. I'm always running the wrong one, so no surprise I mixed them up again.

(2) Should read "look at them to understand" near the end.




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