# RogerBW's Blog

 The units program as a command-line calculator 28 July 2017 The units(1) program is available on many Unix systems (though rarely installed by default). Most people think of it as a simple interactive converter. It's actually much more powerful than that. This is how people expect to use it, entering things at an interactive prompt: ``````\$ units You have: mile You want: km * 1.609344 / 0.62137119 `````` That's useful but very dull. Functions are slightly more promising: ``````\$ units You have: tempF(98.4) You want: tempC 36.888889 `````` But it also works with pure command-line arguments, potentially of some complexity - which of course allows it to be a handy command-line calculator too. Atmospheric pressure in psi: ``````\$ units atmosphere gravity*lb/inch^2 * 14.695949 / 0.068045964 `````` What time will my 3d print finish if I start it now? ``````\$ units \$(date +"%Hhour+%Mminute+%Ssecond")+8hour+19minute "hour;minute;second" 19 hour + 31 minute + 9 second `````` The blackbody temperature of a 100m-radius sphere radiating at 1MW (yes, lots of physical constants are here too): ``````\$ units "(1MW/stefanboltzmann/((100m^2)*4pi))^(1/4)" tempC 71.037224 `````` If you're feeding the output into another programme (because this is Unix and you can do that sort of thing), use --compact to strip off the decoration: ``````\$ units --compact "(1MW/stefanboltzmann/((100m^2)*4pi))^(1/4)" tempC 71.037224 `````` Of course it's extensible. As someone who plays a fair bit of GURPS, I find it useful to implement that game's logarithmic range scale, so I add to my local .units file: ``````gurpsrange(x) units=[1;yard] range=[0,) \ 10^((x+2)/6)*yard ; log(gurpsrange/yard)*6-2 `````` and now I can easily calculate ranges for a space game: ``````\$ units 5astronomicalunit gurpsrange 69.476555 \$ units "gurpsrange(40)" mile * 5681.8182 / 0.000176 `````` For any Torg players: ``````torgdistance(x) units=[1;metre] range=[0,) \ 10^(x/5)*metre ; log(torgdistance/metre)*5 torgtime(x) units=[1;second] range=[0,) \ 10^(x/5)*second ; log(torgtime/second)*5 torgweight(x) units=[1;kg] range=[0,) \ 10^(x/5)*kg ; log(torgweight/kg)*5 torgspeed(x) units=[1;m/s] range=[0,) \ 10^((x-5)/5)*m/s ; log(torgspeed*s/m)*5+5 `````` Note that speed is not distance minus time as it should have been in a cleanly-designed system, but based on metres per 10s combat round; thus the fudge factor. What a pity. Comments on this post are now closed. If you have particular grounds for adding a late comment, comment on a more recent post quoting the URL of this one. Search 10 per page 20 per page 50 per page 100 per page Archive Tags 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s 3d printing action aeronautics aikakirja anecdote animation anime army astronomy audio tech base commerce battletech beer boardgaming bookmonth chain of command children chronicle church of no redeeming virtues cold war comedy computing contemporary cornish smuggler cosmic encounter coup cycling dead of winter doctor who documentary drama driving drone ecchi espionage essen 2015 essen 2016 essen 2017 existential risk falklands war fandom fantasy film firefly first world war flash point food garmin drive gazebo geodata gin gurps gurps 101 harpoon historical history horror hugo 2014 hugo 2015 hugo 2016 hugo 2017 hugo 2018 hugo-nebula reread in brief avoid instrumented life kickstarter learn to play leaving earth linux mecha museum mystery naval non-fiction one for the brow opera perl photography podcast politics powers prediction privacy project woolsack pyracantha quantum rail ranting raspberry pi reading reading boardgames social real life restaurant reviews romance rpg a day rpgs science fiction scythe second world war security shipwreck simutrans smartphone south atlantic war squaddies stationery steampunk stuarts suburbia superheroes suspense television the resistance thirsty meeples thriller tin soldier torg toys trailers travel vietnam war war wargaming weather wives and sweethearts writing about writing x-wing young adult Special All book reviews, All film reviews
Produced by aikakirja v0.1