unitsコマンドは単位から単位の簡易計算に使えるツールです
A4用紙のサイズといった規格から、mからマイルへという変換も簡単にできます
実際のところ
例として3ミリ光秒*1とマイルの対応なんていう
(すくなくとも私は)突然新橋の路上で聞かれても回答できそうもない話も
# units "3 millilightseconds" miles * 558.84719 / 0.0017893979
よく使う規格も定義されてますのでA4のサイズが見たいときには
# units "A4paper" Definition: 210 mm 297 mm = 0.06237 m^2
さらに中々凄まじい事に、日本ローカルな坪や尺貫法、古代ローマの単位なんてのまで定義されています。
# units "4.5 edoma" m2 * 6.9504132 / 0.14387634 # units "4.5 jou_area" m2 * 6.9504132 / 0.14387634
約25枚のA4紙は約1畳(江戸間)!
# units "1 edoma" A4paper * 24.76409 / 0.040381052
何故か指輪のサイズまでわかる
日本規格の指輪の内径サイズまで分かります……ナンデ???
# units "jpringsize(10)" cm * 5.0265482 / 0.19894368
定義をみると……結構複雑なことをやっている
# Japanese sizes start with size 1 at a 13mm inside diameter and each size is # 1|3 mm larger in diameter than the previous one. They are multiplied by pi # to give circumference. jpringsize(n) units=[1;mm] domain=[1,) range=[0.040840704,) \ (38|3 + n/3) pi mm ; 3 jpringsize/ pi mm + (-38)
蛇足
あまりに面白すぎたので日本部分の定義ファイルを転載
# # Traditional Japanese units (shakkanhou) # # The traditional system of weights and measures is called shakkanhou from the # shaku and the ken. Japan accepted SI units in 1891 and legalized conversions # to the traditional system. In 1909 the inch-pound system was also legalized, # so Japan had three legally approved systems. A change to the metric system # started in 1921 but there was a lot of resistance. The Measurement Law of # October 1999 prohibits sales in anything but SI units. However, the old # units still live on in construction and as the basis for paper sizes of books # and tools used for handicrafts. # # Note that units below use the Hepburn romanization system. Some other # systems would render "mou", "jou", and "chou" as "mo", "jo" and "cho". # # # http://hiramatu-hifuka.com/onyak/onyindx.html # Japanese Proportions. These are still in everyday use. They also # get used as units to represent the proportion of the standard unit. wari_proportion 1|10 wari wari_proportion bu_proportion 1|100 # The character bu can also be read fun or bun # but usually "bu" is used for units. rin_proportion 1|1000 mou_proportion 1|10000 # Japanese Length Measures # # The length system is called kanejaku or # square and originated in China. It was # adopted as Japan's official measure in 701 # by the Taiho Code. This system is still in # common use in architecture and clothing. shaku 1|3.3 m mou 1|10000 shaku rin 1|1000 shaku bu_distance 1|100 shaku sun 1|10 shaku jou_distance 10 shaku jou jou_distance kanejakusun sun # Alias to emphasize architectural name kanejaku shaku kanejakujou jou # http://en.wikipedia.org/wiki/Taiwanese_units_of_measurement taichi shaku # http://zh.wikipedia.org/wiki/台尺 taicun sun # http://zh.wikipedia.org/wiki/台制 !utf8 台尺 taichi # via Hanyu Pinyin romanizations 台寸 taicun !endutf8 # In context of clothing, shaku is different from architecture # http://www.scinet.co.jp/sci/sanwa/kakizaki-essay54.html kujirajaku 10|8 shaku kujirajakusun 1|10 kujirajaku kujirajakubu 1|100 kujirajaku kujirajakujou 10 kujirajaku tan_distance 3 kujirajakujou ken 6 shaku # Also sometimes 6.3, 6.5, or 6.6 # http://www.homarewood.co.jp/syakusun.htm # mostly unused chou_distance 60 ken chou chou_distance ri 36 chou # Japanese Area Measures # Tsubo is still used for land size, though the others are more # recognized by their homonyms in the other measurements. gou_area 1|10 tsubo tsubo 36 shaku^2 # Size of two tatami = ken^2 ?? se 30 tsubo tan_area 10 se chou_area 10 tan_area # http://en.wikipedia.org/wiki/Taiwanese_units_of_measurement ping tsubo # http://zh.wikipedia.org/wiki/坪 jia 2934 ping # http://zh.wikipedia.org/wiki/甲_(单位) fen 1|10 jia # http://zh.wikipedia.org/wiki/分 fen_area 1|10 jia # Protection against future collisions !utf8 坪 ping # via Hanyu Pinyin romanizations 甲 jia 分 fen 分地 fen_area # Protection against future collisions !endutf8 # Japanese architecture is based on a "standard" size of tatami mat. # Room sizes today are given in number of tatami, and this number # determines the spacing between colums and hence sizes of sliding # doors and paper screens. However, every region has its own slightly # different tatami size. Edoma, used in and around Tokyo and # Hokkaido, is becoming a nationwide standard. Kyouma is used around # Kyoto, Osaka and Kyuushu, and Chuukyouma is used around Nagoya. # Note that the tatami all have the aspect ratio 2:1 so that the mats # can tile the room with some of them turned 90 degrees. # # http://www.moon2.net/tatami/infotatami/structure.html edoma (5.8*2.9) shaku^2 kyouma (6.3*3.15) shaku^2 chuukyouma (6*3) shaku^2 jou_area edoma tatami jou_area # Japanese Volume Measures # The "shou" is still used for such things as alcohol and seasonings. # Large quantities of paint are still purchased in terms of "to". shaku_volume 1|10 gou_volume gou_volume 1|10 shou gou gou_volume shou (4.9*4.9*2.7) sun^3 # The character shou which is # the same as masu refers to a # rectangular wooden cup used to # measure liquids and cereal. # Sake is sometimes served in a masu # Note that it happens to be # EXACTLY 7^4/11^3 liters. to 10 shou koku 10 to # No longer used; historically a measure of rice # Japanese Weight Measures # # http://wyoming.hp.infoseek.co.jp/zatugaku/zamoney.html # Not really used anymore. rin_weight 1|10 bu_weight bu_weight 1|10 monme fun 1|10 monme monme momme kin 160 monme kan 1000 monme kwan kan # This was the old pronounciation of the unit. # The old spelling persisted a few centuries # longer and was not changed until around # 1950.
参考もと
本の虫: 500マイル以上離れた場所にメールが送れないのだが
man units (1): unit conversion and calculation program
units(1): unit conversion program - Linux man page
*1:なんて単位がある事自体、今の今まで忘れていました