UNITS(1)
NAME
units - conversion program
SYNTAX
units [-f filename] [-q] [to-unit from-unit]
SUMMARY
-f filename
Specifies the name of the units data file to load.
-q Supresses prompting of the user for units and the dis-
play of statistics about the number of units loaded.
from-unit to-unit
Allows a single unit converstion to be done directly
from the command line. No prompting will occur. The
units program will print out only the result of this
single conversion.
DESCRIPTION
The units program converts quantities expression in vari-
ous scales to their equivalents in other scales. The
units program can only handle multiplicative scale
changes. It cannot convert Centigrade to Fahrenheit, for
example. It works interactively by prompting the user for
input:
You have: meters
You want: feet
* 3.2808399
/ 0.3048
You have: cm^3
You want: gallons
* 0.00026417205
/ 3785.4118
Powers of units can be specified using the '^' character
as shown in the example, or by simple concatenation: 'cm3'
is equivalent to 'cm^3'. Multiplication of units can be
specified by using spaces, a dash or an asterisk. Divi-
sion of units is indicated by the slash ('/'). Note that
multiplication has a higher precedence than division, so
If the user enters incompatible unit types, the units pro-
gram will print a message indicating that the units are
not conformable and it will display the reduced form for
each unit:
You have: ergs/hour
You want: fathoms kg^2 / day
conformability error
2.7777778e-11 kg m^2 / sec^3
2.1166667e-05 kg^2 m / sec
The conversion information is read from a units data file.
The default file includes definitions for most familiar
units, abbreviations and metric prefixes. Some constants
of nature included are:
pi ratio of circumference to diameter
c speed of light
e charge on an electron
g acceleration of gravity
force same as g
mole Avogadro's number
water pressure per unit height of water
mercury pressure per unit height of mercury
au astronomical unit
'Pound' is a unit of mass. Compound names are run
together so 'poundforce' is a unit of force. British
units that differ from their US counterparts are prefixed
with 'br', and currency is prefixed with its country name:
'belgiumfranc', 'britainpound'. When searching for a
unit, if the specified string does not appear exactly as a
unit name, then the units program will try to remove a
trailing 's' or a trailing 'es' and check again for a
match.
All of these definitions can be read in the standard units
file, or you can supply your own file. A unit is speci-
fied on a single line by giving its name and an equiva-
lence. One should be careful to define new units in terms
of old ones so that a reduction leads to the primitive
units which are marked with '!' characters. The units
program will not detect infinite loops that could be
caused by careless unit definitions.
Prefixes are defined in the same was as standard units,
but with a trailing dash at the end of the prefix name.
BUGS
The effect of including a '/' in a prefix is surprising.
Exponents entered by the user can be only one digit.
The user must use | to indicate division of numbers and /
to indicate division of symbols. This distinction should
not be necessary.
The program contains various arbitrary limits on the
length of the units converted and on the length of the
data file.
FILES
units.lib - the standard units library
AUTHOR
Adrian Mariano (adrian@u.washington.edu or mari-
ano@geom.umn.edu)