UNITS(1) OpenBSD Reference Manual UNITS(1)NAMEunits - conversion program
SYNOPSISunits [-qv] [-f filename] [from-unit to-unit]
DESCRIPTION
The units program converts quantities expressed in various scales to
their equivalents in other scales. The units program can only handle
multiplicative scale changes. It cannot convert Celsius to Fahrenheit,
for example. It also does not handle logarithmic units such as bels. 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
The units program can handle numbers as well:
You have: 60 miles/hr
You want: km/hr
* 96.56064
/ 0.010356187
You have: 5 austriaschilling
You want: 100 italylira
* 7.0357114
/ 0.14213204
In other words, 60 miles per hour is about 96.6 km/hr, and 5 Austrian
Schillings will get you seven 100-Lira coins.
The options are as follows:
-f filename
Specifies the name of the units data file to load.
-q Suppresses prompting of the user for units and the display of
statistics about the number of units loaded.
-v Prints the version number.
from-unit to-unit
Allows a single unit conversion 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.
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. Division of units is indicated by the slash (`/'). Note that
multiplication has a higher precedence than division, so `m/s/s' is the
same as `m/s^2' or `m/s s'. If the user enters incompatible unit types,
the units program 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 (at 4 C)
mercury pressure per unit height of mercury
ao Bohr radius
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 specified on a single line by giving
its name and an equivalence. 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 way as standard units, but with a
trailing dash at the end of the prefix name. Prefixes are applied after
the longest matching unit name is found; for example, ``nmile'' is taken
to be a nautical mile rather than a nanomile.
FILES
/usr/share/misc/units.lib the standard units library
AUTHORS
Adrian Mariano (adrian@cam.cornell.edu or mariano@geom.umn.edu)
BUGS
The effect of including a `/' in a prefix is surprising.
Exponents of units entered by the user can be only one digit. You can
work around this by multiplying several terms.
The user must use `|' to indicate division of numbers and `/' to indicate
division of symbols. This distinction should not be necessary.
Prefixes specified without a unit are treated as dimensionless
quantities. This can lead to confusion when some prefixes are also
defined as units (e.g., m). For example, Tera- / Giga- is 1000, but one
Tesla (T) is 10,000 Gauss (G).
Some non-SI units have multiple definitions (e.g., barrel, calorie) and
others have changed over time (e.g., cubit). In particular, monetary
values fluctuate.
The program contains various arbitrary limits on the length of the units
converted and on the length of the data file.
The program should use a hash table to store units so that it doesn't
take so long to load the units list and check for duplication.
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9
