conversion program 



units [-f filename] [-qv] [from-unit to-unit]


The units utility converts quantities expressed in various scales to their equivalents in other scales. The units utility can only handle multiplicative scale changes. It cannot convert Celsius 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. 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 Utility displays a message indicating that the units are not conformable and it displays 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 utility tries 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 utility does 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.


-f filename 

specifies the name of the units data file to load.


suppresses prompting of the user for units and the display of statistics about the number of units loaded.


displays the version number.

from-unit to-unit 

allows a single unit conversion to be done directly from the command line. No prompting occurs. The units utility displays only the result of this single conversion.



the standard units library


Adrian Mariano (adrian@cam.cornell.edu or mariano@geom.umn.edu)


The effect of including a / in a prefix is surprising.

Exponents 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.

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.


Possible exit status values are:


Successful completion or a non-usage error occurred.


A usage error occurred.


Windows 8.1. Windows Server 2012 R2. Windows 10. Windows Server 2016. Windows Server 2019. Windows 11. Windows Server 2022.


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