1.\" $FreeBSD$ 2.Dd July 14, 1993 3.Dt UNITS 1 4.Os 5.Sh NAME 6.Nm units 7.Nd conversion program 8.Sh SYNTAX 9.Nm 10.Op Fl f Ar filename 11.Op Fl qv 12.Op Ar to-unit from-unit 13.Sh SUMMARY 14The following options are available: 15.Bl -tag -width indent 16.It Fl f Ar filename 17Specify the name of the units data file to load. 18.It Fl q 19Suppress prompting of the user for units and the display of statistics 20about the number of units loaded. 21.It Fl v 22Print the version number. 23.It Ar from-unit to-unit 24Allow a single unit conversion to be done directly from the command 25line. The program will not print prompts. It will print out the 26result of the single specified conversion. 27.Sh DESCRIPTION 28The 29.Nm 30program converts quantities expressed in various scales to 31their equivalents in other scales. The 32.Nm 33program can only 34handle multiplicative scale changes. It cannot convert Centigrade 35to Fahrenheit, for example. It works interactively by prompting 36the user for input: 37.Bd -literal 38 You have: meters 39 You want: feet 40 * 3.2808399 41 / 0.3048 42 43 You have: cm^3 44 You want: gallons 45 * 0.00026417205 46 / 3785.4118 47 48 You have: meters/s 49 You want: furlongs/fortnight 50 * 6012.8848 51 / 0.00016630952 52 53 You have: 1|2 inch 54 You want: cm 55 * 1.27 56 / 0.78740157 57.Ed 58.Pp 59Powers of units can be specified using the '^' character as shown in 60the example, or by simple concatenation: 'cm3' is equivalent to 'cm^3'. 61Multiplication of units can be specified by using spaces, a dash or 62an asterisk. Division of units is indicated by the slash ('/'). 63Note that multiplication has a higher precedence than division, 64so 'm/s/s' is the same as 'm/s^2' or 'm/s s'. Division of numbers 65must be indicated using the vertical bar ('|'). To convert half a 66meter, you would write '1|2 meter'. If you write '1/2 meter' then the 67units program would interpret that as equivalent to '0.5/meter'. 68If you enter incompatible unit types, the units program will 69print a message indicating that the units are not conformable and 70it will display the reduced form for each unit: 71.Bd -literal 72 You have: ergs/hour 73 You want: fathoms kg^2 / day 74 conformability error 75 2.7777778e-11 kg m^2 / sec^3 76 2.1166667e-05 kg^2 m / sec 77.Ed 78.Pp 79The conversion information is read from a units data file. The default 80file includes definitions for most familiar units, abbreviations and 81metric prefixes. Some constants of nature included are: 82.Pp 83.Bl -inset -offset indent -compact 84.It pi ratio of circumference to diameter 85.It c speed of light 86.It e charge on an electron 87.It g acceleration of gravity 88.It force same as g 89.It mole Avogadro's number 90.It water pressure per unit height of water 91.It mercury pressure per unit height of mercury 92.It au astronomical unit 93.El 94.Pp 95The unit 'pound' is a unit of mass. Compound names are run together 96so 'poundforce' is a unit of force. The unit 'ounce' is also a unit 97of mass. The fluid ounce is 'floz'. British units that differ from 98their US counterparts are prefixed with 'br', and currency is prefixed 99with its country name: 'belgiumfranc', 'britainpound'. When searching 100for a unit, if the specified string does not appear exactly as a unit 101name, then 102.Nm 103will try to remove a trailing 's' or a 104trailing 'es' and check again for a match. 105.Pp 106To find out what units are available read the standard units file. 107If you want to add your own units you can supply your own file. 108A unit is specified on a single line by 109giving its name and an equivalence. Be careful to define 110new units in terms of old ones so that a reduction leads to the 111primitive units which are marked with '!' characters. 112The 113.Nm 114program will not detect infinite loops that could be caused 115by careless unit definitions. Comments in the unit definition file 116begin with a '/' character at the beginning of a line. 117.Pp 118Prefixes are defined in the same was as standard units, but with 119a trailing dash at the end of the prefix name. If a unit is not found 120even after removing trailing 's' or 'es', then it will be checked 121against the list of prefixes. Prefixes will be removed until a legal 122base unit is identified. 123.Pp 124Here is an example of a short units file that defines some basic 125units. 126.Pp 127.Bl -inset -offset indent -compact 128.It m !a! 129.It sec !b! 130.It micro- 1e-6 131.It minute 60 sec 132.It hour 60 min 133.It inch 0.0254 m 134.It ft 12 inches 135.It mile 5280 ft 136.El 137.Sh BUGS 138The effect of including a '/' in a prefix is surprising. 139.Pp 140Exponents entered by the user can be only one digit. 141You can work around this by multiplying several terms. 142.Pp 143The user must use | to indicate division of numbers and / to 144indicate division of symbols. This distinction should not 145be necessary. 146.Pp 147The program contains various arbitrary limits on the length 148of the units converted and on the length of the data file. 149.Pp 150The program should use a hash table to store units so that 151it doesn't take so long to load the units list and check 152for duplication. 153.Sh FILES 154.Bl -tag -width /usr/share/misc/units.lib -compact 155.It Pa /usr/share/misc/units.lib 156the standard units library 157.El 158.Sh AUTHORS 159.An Adrian Mariano Aq adrian@cam.cornell.edu 160