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CentOS 7.0 - man page for units_cur (centos section 1)

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This manual is for GNU Units (version 2.00), which performs units
conversions and units calculations.  A copy of the license is in-
cluded	in  the  section  entitled  ``GNU  Free Documentation Li-
UNITS(1)										 UNITS(1)

cense''.

NAME
       units -- unit conversion and calculation program

SYNOPSIS
       'units' [options] [from-unit [to-unit]]

DESCRIPTION
       The 'units' program converts quantities expressed in various  systems  of  measurement  to
       their  equivalents  in  other  systems of measurement.  Like many similar programs, it can
       handle multiplicative scale changes. It can also  handle  nonlinear  conversions  such  as
       Fahrenheit  to Celsius.	See the examples below.  The program can also perform conversions
       from and to sums of units, such as converting between meters and feet plus inches.

       Beyond simple unit conversions, 'units' can be used as a general-purpose scientific calcu-
       lator that keeps track of units in its calculations.  You can form arbitrary complex math-
       ematical expressions of dimensions including sums, products, quotients, powers,	and  even
       roots  of dimensions.  Thus you can ensure accuracy and dimensional consistency when work-
       ing with long expressions that involve many different units that may  combine  in  complex
       ways.

       The  units are defined in an external data file.  You can use the extensive data file that
       comes with this program, or you can provide your own data file to suit  your  needs.   You
       can also use your own data file to supplement the standard data file.

       Basic operation is simple: you enter the units that you want to convert from and the units
       that you want to convert to.  You can use the program interactively with prompts,  or  you
       can use it from the command line.

INTERACTING WITH UNITS
       To  invoke units for interactive use, type 'units' at your shell prompt.  The program will
       print something like this:

	  Currency exchange rates from 04/23/12
	  2516 units, 85 prefixes, 65 nonlinear units

	  You have:

       At the 'You have:' prompt, type the quantity and units that you are converting from.   For
       example,  if you want to convert ten meters to feet, type '10 meters'.  Next, 'units' will
       print 'You want:'.  You should type the units you want to convert to.  To convert to feet,
       you  would type 'feet'.	If the 'readline' library was compiled in then the tab key can be
       used to complete unit names. See Readline Support for more information  about  'readline'.
       To quit the program press Ctrl-C or Ctrl-D under Unix.  Under Windows press Ctrl-Z.

       The  answer will be displayed in two ways.  The first line of output, which is marked with
       a '*' to indicate multiplication, gives the result of the conversion you have  asked  for.
       The  second  line  of  output,  which is marked with a '/' to indicate division, gives the
       inverse of the conversion factor.  If you convert 10 meters to feet, 'units' will print

	      * 32.808399
	      / 0.03048

       which tells you that 10 meters equals about 32.8 feet.  The second number gives	the  con-
       version	in  the  opposite  direction.  In this case, it tells you that 1 foot is equal to
       about 0.03 dekameters since the dekameter is 10 meters.	It also tells you that 1/32.8  is
       about 0.03.

       The  'units'  program prints the inverse because sometimes it is a more convenient number.
       In the example above, for example, the inverse value is an exact  conversion:  a  foot  is
       exactly 0.03048 dekameters.  But the number given the other direction is inexact.

       If you convert grains to pounds, you will see the following:

	  You have: grains
	  You want: pounds
		  * 0.00014285714
		  / 7000

	  From	the  second line of the output you can immediately see that a grain is equal to a
       seven thousandth of a pound.  This is not so obvious from the first line  of  the  output.
       If you find  the output format  confusing, try using the '--verbose' option:

	  You have: grain
	  You want: aeginamina
		  grain = 0.00010416667 aeginamina
		  grain = (1 / 9600) aeginamina

       If you request a conversion between units that measure reciprocal dimensions, then 'units'
       will display the conversion results with an extra note indicating that reciprocal  conver-
       sion has been done:

	  You have: 6 ohms
	  You want: siemens
		  reciprocal conversion
		  * 0.16666667
		  / 6

       Reciprocal conversion can be suppressed by using the '--strict' option.	As usual, use the
       '--verbose' option to get more comprehensible output:

	  You have: tex
	  You want: typp
		  reciprocal conversion
		  1 / tex = 496.05465 typp
		  1 / tex = (1 / 0.0020159069) typp

	  You have: 20 mph
	  You want: sec/mile
		  reciprocal conversion
		  1 / 20 mph = 180 sec/mile
		  1 / 20 mph = (1 / 0.0055555556) sec/mile

       If you enter 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

       If  you	only want to find the reduced form or definition of a unit, simply press Enter at
       the 'You want:' prompt.	Here is an example:

	  You have: jansky
	  You want:
		  Definition: fluxunit = 1e-26 W/m^2 Hz = 1e-26 kg / s^2

       The output from 'units' indicates that the jansky is defined to be  equal  to  a  fluxunit
       which  in  turn	is  defined to be a certain combination of watts, meters, and hertz.  The
       fully reduced (and in this case somewhat more cryptic) form appears on the far right.

       Some named units are treated as dimensionless in some situations.  These units include the
       radian  and  steradian.	 These	units will be treated as equal to 1 in units conversions.
       Power is equal to torque times angular velocity.  This conversion can only be performed if
       the radian is dimensionless.

	  You have: (14 ft lbf) (12 radians/sec)
	  You want: watts
		  * 227.77742
		  / 0.0043902509

       Named dimensionless units are not treated as dimensionless in other contexts.  They cannot
       be used as exponents so for example, 'meter^radian' is not allowed.

       If you want a list of options you can type '?'  at the 'You want:'  prompt.   The  program
       will  display a list of named units that are conformable with the unit that you entered at
       the 'You have:' prompt above.  Conformable unit combinations will not appear on this list.

       Typing 'help' at either prompt displays a short help message.  You can  also  type  'help'
       followed  by  a	unit  name.  This will invoke a pager on the units data base at the point
       where that unit is defined.  You can read the definition and comments that may  give  more
       details or historical information about the unit.  (You can generally quit out of the page
       by pressing 'q'.)

       Typing 'search' text will display a list of all of the units whose names contain text as a
       substring  along  with their definitions.  This may help in the case where you aren't sure
       of the right unit name.

USING UNITS NON-INTERACTIVELY
       The 'units' program can perform units conversions non-interactively from the command line.
       To  do  this,  type the command, type the original unit expression, and type the new units
       you want.  If a units expression contains non-alphanumeric characters,  you  may  need  to
       protect it from interpretation by the shell using single or double quote characters.

       If you type

	  units "2 liters" quarts

       then 'units' will print

	      * 2.1133764
	      / 0.47317647

       and  then  exit.  The output tells you that 2 liters is about 2.1 quarts, or alternatively
       that a quart is about 0.47 times 2 liters.

       If the conversion is successful, then 'units' will return success (zero)  to  the  calling
       environment.  If you enter  non-conformable units then 'units' will print a message giving
       the reduced form of each unit and it will return failure (nonzero) to the calling environ-
       ment.

       When  you  invoke  'units' with only one argument, it will print out the definition of the
       specified unit.	It will return failure if the unit is not defined and success if the unit
       is defined.

UNIT DEFINITIONS
       The   conversion   information	is   read   from   a  units  data  file  that  is  called
       'definitions.units' and is usually located in the '/usr/share/units'  directory.   If  you
       invoke 'units' with the '-V' option, it will print the location of this file.  The default
       file includes definitions for all familiar units, abbreviations and metric  prefixes.   It
       also includes many obscure or archaic units.

       Many constants of nature are defined, including these:

	  pi	      ratio of circumference to diameter
	  c	      speed of light
	  e	      charge on an electron
	  force       acceleration of gravity
	  mole	      Avogadro's number
	  water       pressure per unit height of water
	  Hg	      pressure per unit height of mercury
	  au	      astronomical unit
	  k	      Boltzman's constant
	  mu0	      permeability of vacuum
	  epsilon0    permittivity of vacuum
	  G	      Gravitational constant
	  mach	      speed of sound

       The  standard  data file includes atomic masses for all of the elements and numerous other
       constants.  Also included are the densities of various ingredients used in baking so  that
       '2  cups flour_sifted' can be converted to 'grams'.  This is not an exhaustive list.  Con-
       sult the units data file to see the complete list, or to  see  the  definitions	that  are
       used.

       The  'pound'  is  a  unit  of  mass.   To get force, multiply by the force conversion unit
       'force' or use the shorthand 'lbf'.  (Note that 'g'  is	already  taken	as  the  standard
       abbreviation  for the gram.)  The unit 'ounce' is also a unit of mass.  The fluid ounce is
       'fluidounce' or 'floz'.	British capacity units that differ from  their	US  counterparts,
       such  as  the  British Imperial gallon, are prefixed with 'br'.	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', 'es'.  Next units will replace
       a trailing 'ies' with 'y'.  If that fails, 'units' will check for a prefix.  The  database
       includes  all  of the standard metric prefixes.	Only one prefix is permitted per unit, so
       'micromicrofarad' will fail.  However, prefixes can appear alone with  no  unit	following
       them, so 'micro*microfarad' will work, as will 'micro microfarad'.

       To  find  out  which  units and prefixes are available, read the standard units data file,
       which is extensively annotated.

   English Customary Units
       English customary units differ in various ways in different regions.  In Britain a complex
       system of volume measurements featured different gallons for different materials such as a
       wine gallon and ale gallon that different by twenty percent.  This  complexity  was  swept
       away  in 1824 by a reform that created an entirely new gallon, the British Imperial gallon
       defined as the volume occupied by ten pounds of water.  Meanwhile in the USA the gallon is
       derived	from  the  1707 Winchester wine gallon, which is 231 cubic inches.  These gallons
       differ by about twenty percent.	By default if 'units' runs in the 'en_GB' locale you will
       get  the  British  volume  measures.  If it runs in the 'en_US' locale you will get the US
       volume measures.  In other locales the default values are the US definitions.  If you wish
       to force different definitions then set the environment variable 'UNITS_ENGLISH' to either
       'US' or 'GB' to set the desired definitions independent of the locale.

       Before 1959, the value of a yard (and other units of measure defined in terms of it)  dif-
       fered slightly among English-speaking countries.  In 1959, Australia, Canada, New Zealand,
       the United Kingdom, the United States, and South Africa	adopted  the  Canadian	value  of
       1 yard  =  0.9144 m  (exactly), which was approximately halfway between the values used by
       the UK and the US; it had the additional advantage of making 1 inch =  2.54 cm  (exactly).
       This  new  standard was termed the International Yard.  Australia, Canada, and the UK then
       defined all customary lengths in terms of the International Yard (Australia did not define
       the furlong or rod); because many US land surveys were in terms of the pre-1959 units, the
       US continued to define customary surveyors' units (furlong, chain, rod, and link) in terms
       of the previous value for the foot, which was termed the US survey foot.  The US defined a
       US survey mile as 5280 US survey feet, and defined a statute mile as  a	US  survey  mile.
       The US values for these units differ from the international values by about 2 ppm.

       The  'units'  program  uses the international values for these units; the US values can be
       obtained by using either the 'US' or the 'survey' prefix.   In  either  case,  the  simple
       familiar relationships among the units are maintained, e.g., 1 'furlong' = 660 'ft', and 1
       'USfurlong' = 660 'USft', though the metric equivalents differ slightly	between  the  two
       cases.	The  'US'  prefix or the 'survey' prefix can also be used to obtain the US survey
       mile and the value of the US yard prior to 1959, e.g., 'USmile' or 'surveymile'	(but  not
       'USsurveymile').   To  get the US value of the statute mile, use either 'USstatutemile' or
       'USmile'.

       Except for distances that extend over hundreds of miles (such as in  the  US  State  Plane
       Coordinate System), the differences in the miles are usually insignificant:

	  You have: 100 surveymile - 100 mile
	  You want: inch
		  * 12.672025
		  / 0.078913984

       The pre-1959 UK values for these units can be obtained with the prefix 'UK'.

       In the US, the acre is officially defined in terms of the US survey foot, but 'units' uses
       a definition based on the international foot.  If  you  want  the  official  US	acre  use
       'USacre'  and  similarly  use  'USacrefoot' for the official US version of that unit.  The
       difference between these units is about 4 parts per million.

UNIT EXPRESSIONS
   Operators
       You can enter more complicated units by combining units with operations	such  as  powers,
       multiplication,	division,  addition,  subtraction, and parentheses for grouping.  You can
       use the customary symbols for these operators when 'units' is  invoked  with  its  default
       options.   Additionally,  'units' supports some extensions, including high priority multi-
       plication using a space, and a high priority numerical
	division operator ('|') that can simplify some expressions.

       Powers of units can be specified using the '^' character as shown in the  following  exam-
       ple, or by simple concatenation of a unit and its exponent: 'cm3' is equivalent to 'cm^3';
       if the exponent is more than one digit, the '^' is required.  An exponent like '2^3^2'  is
       evaluated  right  to  left  as usual.  The '^' operator has the second highest precedence.
       You can also use '**' as an exponent operator.

	  You have: cm^3
	  You want: gallons
		  * 0.00026417205
		  / 3785.4118

	  You have: arabicfoot * arabictradepound * force
	  You want: ft lbf
		  * 0.7296
		  / 1.370614

       You multiply units using a space or an asterisk	('*').	 The  example  above  shows  both
       forms.  You can divide units using the slash ('/') or with 'per'.

	  You have: furlongs per fortnight
	  You want: m/s
		  * 0.00016630986
		  / 6012.8727

       When  a	unit  includes	a  prefix,  exponent  operators  apply	to  the  combination,  so
       'centimeter^3' gives cubic centimeters.	If you separate the prefix from the unit with any
       multiplication operator, such as 'centi meter^3', then the prefix is treated as a separate
       unit, so the exponent does not apply.  The second example would be a hundredth of a  cubic
       meter, not a centimeter.

       Multiplication  using  a space  has a higher precedence than division using a slash and is
       evaluated left to right; in effect, the first '/' character marks  the  beginning  of  the
       denominator  of	a unit expression.  This makes it simple to enter a quotient with several
       terms in the denominator: 'W / m^2 Hz'.	If you multiply with '*' then you must group  the
       terms in the denominator with parentheses: 'W / (m^2 * Hz)'.

       The  higher precedence of the space operator may not always be advantageous.  For example,
       'm/s s/day' is equivalent to 'm / s s day' and has dimensions of length	per  time  cubed.
       Similarly, '1/2 meter' refers to a unit of reciprocal length equivalent to 0.5/meter, per-
       haps not what you would intend if you  entered  that  expression.   The	'*'  operator  is
       convenient  for	multiplying  a sequence of quotients.  With the '*' operator, the example
       above becomes 'm/s * s/day', which is equivalent to 'm/day'.  Similarly, you  could  write
       '1/2  *	meter' to get half a meter.  Alternatively, parentheses can be used for grouping:
       you could write '(1/2) meter' to get half a meter.  See Complicated Unit  Expressions  for
       an illustration of the various options.

       The  'units'  program  supports	another option for numerical fractions.  You can indicate
       division of numbers with the vertical bar ('|'), so if you wanted half a meter  you  could
       write  '1|2 meter'.  This operator has the highest precedence, so you can write the square
       root of two thirds '2|3^1|2'.  You cannot use the vertical bar  to  indicate  division  of
       non-numerical units (e.g., 'm|s' results in an error message).

	  You have: 1|2 inch
	  You want: cm
		  * 1.27
		  / 0.78740157

       You can use parentheses for grouping:

	  You have: (1/2) kg / (kg/meter)
	  You want: league
		  * 0.00010356166
		  / 9656.0833

   Sums and Differences of Units
       Outside	of  the  SI, it is sometimes desirable to add values of different units.  You may
       also wish to use 'units' as a calculator that keeps track of units.  Sums  of  conformable
       units are written with the '+' character, and differences with the '-' character.

	  You have: 2 hours + 23 minutes + 32 seconds
	  You want: seconds
		  * 8612
		  / 0.00011611705

	  You have: 12 ft + 3 in
	  You want: cm
		  * 373.38
		  / 0.0026782366

	  You have: 2 btu + 450 ft lbf
	  You want: btu
		  * 2.5782804
		  / 0.38785542

       The expressions that are added or subtracted must reduce to identical expressions in prim-
       itive units, or an error message will be displayed:

	  You have: 12 printerspoint - 4 heredium
						^
	  Illegal sum of non-conformable units

       As usual, the precedence for '+' and '-' is lower than that of  the  other  operators.	A
       fractional quantity such as 2 1/2 cups can be given as '(2+1|2) cups'; the parentheses are
       necessary because multiplication has higher precedence than addition.   If  you	omit  the
       parentheses, 'units' attempts to add '2' and '1|2 cups', and you get an error message:

	  You have: 2+1|2 cups
			     ^
	  Illegal sum or difference of non-conformable units

       The  expression	could  also  be correctly written as '(2+1/2) cups'.  If you write '2 1|2
       cups' the space is interpreted as multiplication so the result is the same as '1 cup'.

       The '+' and '-' characters sometimes appears in exponents like '3.43e+8'.  This	leads  to
       an  ambiguity in an expression like '3e+2 yC'.  The unit 'e' is a small unit of charge, so
       this can be regarded as equivalent to '(3e+2) yC' or '(3 e)+(2 yC)'.   This  ambiguity  is
       resolved by always interpreting '+' and '-' as part of an exponent if possible.

   Numbers as Units
       For  'units', numbers are just another kind of unit.  They can appear as many times as you
       like and in any order in a unit expression.  For example, to find the volume of a box that
       is 2 ft by 3 ft by 12 ft in steres, you could do the following:

	  You have: 2 ft 3 ft 12 ft
	  You want: stere
		  * 2.038813
		  / 0.49048148

	  You have: $ 5 / yard
	  You want: cents / inch
		  * 13.888889
		  / 0.072

       And  the  second example shows how the dollar sign in the units conversion can precede the
       five.  Be careful: 'units' will interpret '$5' with no space as equivalent to 'dollar^5'.

   Built-in Functions
       Several built-in functions are provided: 'sin', 'cos', 'tan', 'ln', 'log', 'log2',  'exp',
       'acos',	'atan' and 'asin'.  The 'sin', 'cos', and 'tan' functions require either a dimen-
       sionless argument or an argument with dimensions of angle.

	  You have: sin(30 degrees)
	  You want:
		  Definition: 0.5

	  You have: sin(pi/2)
	  You want:
		  Definition: 1

	  You have: sin(3 kg)
			    ^
	  Unit not dimensionless

       The other functions on the list require dimensionless arguments.  The inverse  trigonomet-
       ric functions return arguments with dimensions of angle.

       If you wish to take roots of units, you may use the 'sqrt' or 'cuberoot' functions.  These
       functions require that the argument have the appropriate  root.	 You  can  obtain  higher
       roots by using fractional exponents:

	  You have: sqrt(acre)
	  You want: feet
		  * 208.71074
		  / 0.0047913202

	  You have: (400 W/m^2 / stefanboltzmann)^(1/4)
	  You have:
		  Definition: 289.80882 K

	  You have: cuberoot(hectare)
				    ^
	  Unit not a root

   Complicated Unit Expressions
       The 'units' program is especially helpful in ensuring accuracy and dimensional consistency
       when converting lengthy unit expressions.  For example, one  form  of  the  Darcy-Weisbach
       fluid-flow equation is

	    Delta P = (8 / pi)^2 (rho fLQ^2) / d^5,

       where  Delta  P	is  the  pressure drop, rho is the mass density, f is the (dimensionless)
       friction factor, L is the length of the pipe, Q is the volumetric flow rate, and d is  the
       pipe diameter.  It might be desired to have the equation in the form

	    Delta P = A1 rho fLQ^2 / d^5

       that accepted the user's normal units; for typical units used in the US, the required con-
       version could be something like

	  You have: (8/pi^2)(lbm/ft^3)ft(ft^3/s)^2(1/in^5)
	  You want: psi
		  * 43.533969
		  / 0.022970568

       The parentheses allow individual terms in the expression to be entered naturally, as  they
       might  be read from the formula.  Alternatively, the multiplication could be done with the
       '*' rather than a space; then parentheses are needed only around 'ft^3/s' because  of  its
       exponent:

	  You have: 8/pi^2 * lbm/ft^3 * ft * (ft^3/s)^2 /in^5
	  You want: psi
		  * 43.533969
		  / 0.022970568

       Without	parentheses,  and  using spaces for multiplication, the previous conversion would
       need to be entered as

	  You have: 8 lb ft ft^3 ft^3 / pi^2 ft^3 s^2 in^5
	  You want: psi
		  * 43.533969
		  / 0.022970568

   Backwards Compatibility:
       '*' and '-' The original 'units' assigned multiplication a higher precedence than division
       using  the slash.  This differs from the usual precedence rules, which give multiplication
       and division equal precedence, and can be confusing for people who think  of  units  as	a
       calculator.

       The  star operator ('*') included in this 'units' program has, by default, the same prece-
       dence as division, and hence follows the usual precedence rules.  For  backwards  compati-
       bility  you  can invoke 'units' with the '--oldstar' option.  Then '*' has a higher prece-
       dence than division, and the same precedence as multiplication using the space.

       Historically, the hyphen ('-') has been used in technical publications to  indicate  prod-
       ucts  of  units, and the original 'units' program treated it as a multiplication operator.
       Because 'units' provides several other ways to obtain unit products, and because '-' is	a
       subtraction  operator in general algebraic expressions, 'units' treats the binary '-' as a
       subtraction operator by default.  For backwards compatibility use the '--product'  option,
       which  causes 'units' to treat the binary '-' operator as a product operator.  When '-' is
       a multiplication operator it has the same precedence as multiplication with a space,  giv-
       ing it a higher precedence than division.

       When  '-'  is  used as a unary operator it negates its operand.	Regardless of the 'units'
       options, if '-' appears after '(' or after '+' then it will act as  a  negation	operator.
       So  you	can  always  compute  20  degrees  minus 12 minutes by entering '20 degrees + -12
       arcmin'.  You must use this construction when you define new units because you cannot know
       what options will be in force when your definition is processed.

NONLINEAR UNIT CONVERSIONS
       Nonlinear  units  are represented using functional notation.  They make possible nonlinear
       unit conversions such as temperature.

   Temperature Conversions
       Conversions between temperatures are different from linear conversions between temperature
       increments--see	the  example  below.  The absolute temperature conversions are handled by
       units starting with 'temp', and you must use functional notation.  The  temperature-incre-
       ment  conversions  are  done using units starting with 'deg' and they do not require func-
       tional notation.

	  You have: tempF(45)
	  You want: tempC
		  7.2222222

	  You have: 45 degF
	  You want: degC
		  * 25
		  / 0.04

       Think of 'tempF(x)' not as a function but as a notation that indicates that x should  have
       units  of  'tempF'  attached  to  it.  See Defining Nonlinear Units.  The first conversion
       shows that if it's 45 degrees Fahrenheit outside, it's 7.2 degrees  Celsius.   The  second
       conversion  indicates that a change of 45 degrees Fahrenheit corresponds to a change of 25
       degrees Celsius.  The conversion from 'tempF(x)' is to absolute temperature, so that

	  You have: tempF(45)
	  You want: degR
		  * 504.67
		  / 0.0019814929

       gives the same result as

	  You have: tempF(45)
	  You want: tempR
		  * 504.67
		  / 0.0019814929

       But if you convert 'tempF(x)' to 'degC', the output is probably not what you expect:

	  You have: tempF(45)
	  You want: degC
		  * 280.37222
		  / 0.0035666871

       The result is the temperature in K, because 'degC' is defined as 'K', the Kelvin. For con-
       sistent	results,  use the 'tempX' units when converting to a temperature rather than con-
       verting a temperature increment.

   Other Nonlinear Units
       Some other examples of nonlinear units are numerous different ring sizes and wire  gauges,
       the grit sizes used for abrasives, the decibel scale, shoe size, scales for the density of
       sugar (e.g. baume).  The standard data file also supplies units for computing the area  of
       a  circle  and the volume of a sphere.  See the standard units data file for more details.
       Wire gauges with multiple zeroes are signified using negative numbers where two zeroes  is
       '-1'.   Alternatively,  you can use the synonyms 'g00', 'g000', and so on that are defined
       in the standard units data file.

	  You have: wiregauge(11)
	  You want: inches
		  * 0.090742002
		  / 11.020255

	  You have: brwiregauge(g00)
	  You want: inches
		  * 0.348
		  / 2.8735632

	  You have: 1 mm
	  You want: wiregauge
		  18.201919

	  You have: grit_P(600)
	  You want: grit_ansicoated
		  342.76923

       The last example shows the conversion from P graded sand  paper,  which	is  the  European
       standard and may be marked ``P600'' on the back, to the USA standard.

       You can compute the area of a circle using the nonlinear unit, 'circlearea'.  You can also
       do this using the circularinch or circleinch.  The next example shows two ways to  compute
       the area of a circle with a five inch radius and one way to compute the volume of a sphere
       with a radius of one meter.

	  You have: circlearea(5 in)
	  You want: in2
		  * 78.539816
		  / 0.012732395

	  You have: 10^2 circleinch
	  You want: in2
		  * 78.539816
		  / 0.012732395

	  You have: spherevol(meter)
	  You want: ft3
		  * 147.92573
		  / 0.0067601492

UNIT LISTS: CONVERSION TO SUMS OF UNITS
       Outside of the SI, it is sometimes desirable to convert a single unit to a sum of  units--
       for example, feet to feet plus inches.  The conversion from sums of units was described in
       Sums and Differences of Units and is a simple matter of adding  the  units  with  the  '+'
       sign:

	  You have: 12 ft + 3 in + 3|8 in
	  You want: ft
		  * 12.28125
		  / 0.081424936

       Although  you can similarly write a sum of units to convert to, the result will not be the
       conversion to the units in the sum, but rather the conversion to the particular	sum  that
       you have entered:

	  You have: 12.28125 ft
	  You want: ft + in + 1|8 in
		  * 11.228571
		  / 0.089058524

       The unit expression given at the 'You want:' prompt is equivalent to asking for conversion
       to multiples of '1 ft + 1 in + 1|8 in', which is 1.09375 ft, so the conversion in the pre-
       vious example is equivalent to

	  You have: 12.28125 ft
	  You want: 1.09375 ft
		  * 11.228571
		  / 0.089058524

       In  converting  to  a  sum  of  units  like miles, feet and inches, you typically want the
       largest integral value for the first unit, followed by the largest integral value for  the
       next,  and  the	remainder  converted to the last unit.	You can do this conversion easily
       with 'units' using a special syntax for lists of units.	You must list the  desired  units
       in order from largest to smallest, separated by the semicolon (';') character:

	  You have: 12.28125 ft
	  You want: ft;in;1|8 in
		  12 ft + 3 in + 3|8 in

       The conversion always gives integer coefficients on the units in the list, except possibly
       the last unit when the conversion is not exact:

	  You have: 12.28126 ft
	  You want: ft;in;1|8 in
		  12 ft + 3 in + 3.00096 * 1|8 in

       The order in which you list the units is important:

	  You have: 3 kg
	  You want: oz;lb
		  105 oz + 0.051367866 lb

	  You have: 3 kg
	  You want: lb;oz
		  6 lb + 9.8218858 oz

       Listing ounces before pounds produces a technically correct result, but not a very  useful
       one.   You must list the units in descending order of size in order to get the most useful
       result.

       Ending a unit list with the separator ';' has the same effect as repeating the  last  unit
       on  the list, so 'ft;in;1|8 in;' is equivalent to 'ft;in;1|8 in;1|8 in'.  With the example
       above, this gives

	  You have: 12.28126 ft
	  You want: ft;in;1|8 in;
		  12 ft + 3 in + 3|8 in + 0.00096 * 1|8 in

       in effect separating the integer and fractional parts of  the  coefficient  for	the  last
       unit.   If  you instead prefer to round the last coefficient to an integer you can do this
       with the '--round' ('-r') option.  With the previous example, the result is

	  You have: 12.28126 ft
	  You want: ft;in;1|8 in
		  12 ft + 3 in + 3|8 in (rounded down to nearest 1|8 in)

       When you use the '-r' option, repeating the last unit on the list  has  no  effect  (e.g.,
       'ft;in;1|8  in;1|8  in'	is equivalent to 'ft;in;1|8 in'), and hence neither does ending a
       list with a ';'.  With a single unit and the '-r' option, a  terminal  ';'  does  have  an
       effect:	it  causes 'units' to treat the single unit as a list and produce a rounded value
       for the single unit.  Without the extra ';', the '-r' option has no effect on single  unit
       conversions.  This example shows the ouput using the '-r' option:

	  You have: 12.28126 ft
	  You want: in
		  * 147.37512
		  / 0.0067854058

	  You have: 12.28126 ft
	  You want: in;
		  147 in (rounded down to nearest in)

       Each  unit  that  appears in the list must be conformable with the first unit on the list,
       and of course the listed units must also be comformable with the You have  unit	that  you
       enter.

	  You have: meter
	  You want: ft;kg
		       ^
	  conformability error
		  ft = 0.3048 m
		  kg = 1 kg

	  You have: meter
	  You want: lb;oz
	  conformability error
		  1 m
		  0.45359237 kg

       In  the	first case, 'units' reports the disagreement between units appearing on the list.
       In the second case, 'units' reports disagreement between the  unit  you	entered  and  the
       desired	conversion.   This  conformability  error  is based on the first unit on the unit
       list.

       Other common candidates for conversion to sums of units are angles and time:

	  You have: 23.437754 deg
	  You want; deg;arcmin;arcsec
	      23 deg + 26 arcmin + 15.9144 arcsec

	      You have: 7.2319 hr
	      You want: hr;min;sec
		  7 hr + 13 min + 54.84 sec

       In North America, recipes for cooking typically measure ingredients  by	volume,  and  use
       units  that  are  not  always convenient multiples of each other.  Suppose that you have a
       recipe for 6 and you wish to make a portion for 1.  If the recipe calls for 2 1/2 cups  of
       an  ingredient,	you might wish to know the measurements in terms of measuring devices you
       have available, you could use 'units' and enter

	  You have: (2+1|2) cup / 6
	  You want: cup;1|2 cup;1|3 cup;1|4 cup;tbsp;tsp;1|2 tsp;1|4 tsp
		  1|3 cup + 1 tbsp + 1 tsp

       By default, if a unit in a list begins with fraction of the form 1|x and its multiplier is
       an  integer, the fraction is given as the product of the multiplier and the numerator; for
       example,

	  You have: 12.28125 ft
	  You want: ft;in;1|8 in;
		  12 ft + 3 in + 3|8 in

       In many cases, such as the example above, this is what is wanted, but sometimes it is not.
       For  example,  a  cooking  recipe for 6 might call for 5 1/4 cup of an ingredient, but you
       want a portion for 2, and your 1-cup measure is not available; you might try

	  You have: (5+1|4) cup / 3
	  You want: 1|2 cup;1|3 cup;1|4 cup
		  3|2 cup + 1|4 cup

       This result might be fine for a baker who has a	1 1/2-cup  measure  (and  recognizes  the
       equivalence),  but  it  may not be as useful to someone with more limited set of measures,
       who does want to do additional calculations, and only wants to  know  ``How  many  1/2-cup
       measures  to  I	need  to  add?''   After  all,	that's what was actually asked.  With the
       '--show-factor' option, the factor will not be combined with a unity  numerator,  so  that
       you get

	  You have: (5+1|4) cup / 3
	  You want: 1|2 cup;1|3 cup;1|4 cup
		  3 * 1|2 cup + 1|4 cup

       A  user-specified  fractional unit with a numerator other than 1 is never overridden, how-
       ever--if a unit list specifies '3|4 cup;1|2 cup', a result equivalent to 1 1/2  cups  will
       always be shown as '2 * 3|4 cup' whether or not the '--show-factor' option is given.

       Some  applications  for	unit  lists  may be less obvious.  Suppose that you have a postal
       scale and wish to ensure that it's accurate at 1 oz,  but  have	only  metric  calibration
       weights.  You might try

	  You have: 1 oz
	  You want: 100 g;50 g; 20 g;10 g;5 g;2 g;1 g;
		  20 g + 5 g + 2 g + 1 g + 0.34952312 * 1 g

       You might then place one each of the 20 g, 5 g, 2 g, and 1 g weights on the scale and hope
       that it indicates close to

	  You have: 20 g + 5 g + 2 g + 1 g
	  You want: oz;
		  0.98767093 oz

       Appending ';' to 'oz' forces a one-line display that includes the unit; here  the  integer
       part of the result is zero, so it is not displayed.

       A unit list such as

	  cup;1|2 cup;1|3 cup;1|4 cup;tbsp;tsp;1|2 tsp;1|4 tsp

       can  be	tedious  to  enter.  The 'units' program provides shorthand names for some common
       combinations:

	  hms	      hours, minutes, seconds
	  dms	      angle: degrees, minutes, seconds
	  time	      years, days, hours, minutes and seconds
	  usvol       US cooking volume: cups and smaller

       Using these shorthands, or unit list aliases, you can do the following conversions:

	  You have: anomalisticyear
	  You want: time
		  1 year + 25 min + 3.4653216 sec
	  You have: 1|6 cup
	  You want: usvol
		  2 tbsp + 2 tsp

       You cannot combine a unit list alias with other units: it must appear alone  at	the  'You
       want:' prompt.

       You  can  display  the  definition  of a unit list alias by entering it at the 'You have:'
       prompt:

	  You have: dms
		  Definition: unit list, deg;arcmin;arcsec

       When you specify compact output with '--compact', '--terse' or '-t' and perform conversion
       to  a unit list, 'units' lists the conversion factors for each unit in the list, separated
       by semicolons.

	  You have: year
	  You want: day;min;sec
	  365;348;45.974678

       Unlike the case of regular output, zeros are included in this output list:

	  You have: liter
	  You want: cup;1|2 cup;1|4 cup;tbsp
	  4;0;0;3.6280454

INVOKING UNITS
       You invoke 'units' like this:

	  units [options] [from-unit [to-unit]]

       If the from-unit and to-unit are omitted, then the program will use interactive prompts to
       determine  which  conversions to perform.  See Interactive Use.	If both from-unit and to-
       unit are given, 'units' will print the result of that single conversion and then exit.  If
       only  from-unit	appears  on the command line, 'units' will display the definition of that
       unit and exit.  Units specified on the command line may need to be quoted to protect  them
       from shell interpretation and to group them into two arguments.	See Command Line Use.

       The  following  options	allow  you to read in an alternative units file, check your units
       file, or change the output format:

       -c, --check
	      Check that all units and prefixes defined in the units data file reduce  to  primi-
	      tive  units.   Print a list of all units that cannot be reduced.	Also display some
	      other diagnostics about suspicious definitions in the units data file.  Only  defi-
	      nitions  active  in  the current locale are checked.  You should always run 'units'
	      with this option after modifying a units data file.

       --check-verbose, --verbose-check
	      Like the '--check' option, this option prints  a	list  of  units  that  cannot  be
	      reduced.	But to help find unit  definitions that cause endless loops, it lists the
	      units as they are checked.  If 'units' hangs, then the last unit to be printed  has
	      a bad definition.  Only definitions active in the current locale are checked.

       -o format, --output-format format
	      Use the specified format for numeric output; the format is a subset of that for the
	      printf function in the ANSI C standard.  Only a numeric format ('E' or 'e' for sci-
	      entific  notation, 'f' for fixed-point decimal, or 'G' or 'g' to specify the number
	      of significant figures) is allowed.  The default format is '%.8g'; for greater pre-
	      cision, you could specify '-o %.15g'.  See Numeric Output Format and the documenta-
	      tion for printf() for more detailed descriptions of the format specification.

       -e, --exponential
	      Set the numeric output format to exponential (i.e., scientific notation), like that
	      used in the Unix 'units' program.

       -f filename, --file filename
	      Instruct 'units' to load the units file 'filename'.  You can specify up to 25 units
	      files on the command line.  When you use this option, 'units' will  load	only  the
	      files you list on the command line; it will not load the standard file or your per-
	      sonal units file unless you explicitly list them.  If filename is the empty  string
	      ('-f ""'), the default units file (or that specified by 'UNITSFILE') will be loaded
	      in addition to any others specified with '-f'.

       -h, --help
	      Print out a summary of the options for 'units'.

       -m, --minus
	      Causes '-' to be interpreted as a subtraction operator.  This is the default behav-
	      ior.

       -p, --product
	      Causes '-' to be interpreted as a multiplication operator when it has two operands.
	      It will act as a negation operator when  it  has	only  one  operand:  '(-3)'.   By
	      default '-' is treated as a subtraction operator.

       --oldstar
	      Causes '*' to have the old-style precedence, higher than the precedence of division
	      so that '1/2*3' will equal '1/6'.

       --newstar
	      Forces '*' to have the new (default) precedence that follows  the  usual	rules  of
	      algebra:	the  precedence  of  '*'  is  the  same as the precedence of '/', so that
	      '1/2*3' will equal '3/2'.

       --compact
	      Give compact output featuring only the  conversion  factor.   This  turns  off  the
	      '--verbose' option.

       -q, --quiet, --silent
	      Suppress	prompting  of  the user for units and the display of statistics about the
	      number of units loaded.

       -n, --nolists
	      Disable conversion to unit lists.

       -r, --round
	      When converting to a combination of units given by a unit list, round the value  of
	      the last unit in the list to the nearest integer.

       -S, --show-factor
	      When  converting	to a combination of units specified in a list, always show a non-
	      unity factor before a unit that begins with a fraction with  a  unity  denominator.
	      By default, if the unit in a list begins with fraction of the form 1|x and its mul-
	      tiplier is an integer other than 1, the fraction is given as  the  product  of  the
	      multiplier  and  the  numerator (e.g., '3|8 in' rather than '3 * 1|8 in').  In some
	      cases, this is not what is wanted; for example, the results for  a  cooking  recipe
	      might  show  '3 * 1|2 cup' as '3|2 cup'.	With the '--show-factor' option, a result
	      equivalent to 1.5 cups will display as '3 * 1|2 cup'  rather  than  '3|2	cup'.	A
	      user-specified  fractional  unit with a numerator other than 1 is never overridden,
	      however--if a unit list specifies '3|4 cup;1|2 cup', a result equivalent	to  1 1/2
	      cups  will  always  be  shown  as  '2 * 3|4 cup' whether or not the '--show-factor'
	      option is given.

       -s, --strict
	      Suppress conversion of units to their reciprocal units.  For example, 'units'  will
	      normally	convert  hertz	to  seconds  because  these units are reciprocals of each
	      other.  The strict option requires that units be strictly conformable to perform	a
	      conversion, and will give an error if you attempt to convert hertz to seconds.

       -1, --one-line
	      Give  only  one  line of output (the forward conversion).  Do not print the reverse
	      conversion.  If a reciprocal conversion is performed then 'units' will still  print
	      the ``reciprocal conversion'' line.

       -t, --terse
	      Give  terse  output  when  converting  units.  This option can be used when calling
	      'units' from another program so that the output is easy to parse.  This option  has
	      the   combined   effect	of   these  options:  '--strict'  '--quiet'  '--one-line'
	      '--compact'.

       -v, --verbose
	      Give slightly more verbose output when converting units.	When  combined	with  the
	      '-c' option this gives the same effect as '--check-verbose'.

       -V, --version
	      Print  program  version  number,	tell  whether  the  'readline'	library  has been
	      included, and give the location of the default units data file.

       -l locale, --locale locale
	      Force a specified locale such as 'en_GB' to get  British	definitions  by  default.
	      This overrides the locale determined from system settings or environment variables.
	      See Locale for a description of locale format.

ADDING YOUR OWN DEFINITIONS
   Units Data Files
       The units and prefixes that 'units' can convert are defined in the units data file,  typi-
       cally  '/usr/share/units/definitions.units'.   Although you can extend or modify this data
       file if you have appropriate user privileges, it's usually better  to  put  extensions  in
       separate files so that the definitions will be preserved when you update 'units'.

       You  can  include additional data files in the units database using the '!include' command
       in the standard units data file. For example

	  !include    /usr/local/share/units/local.units

       might be appropriate for  a  site-wide  supplemental  data  file.   The	location  of  the
       '!include'  statement  in  the  standard  units	data file is important; later definitions
       replace earlier ones, so any definitions in an included	file  will  override  definitions
       before  the '!include' statement in the standard units data file.  With normal invocation,
       no warning is given about redefinitions; to ensure  that  you  don't  have  an  unintended
       redefinition, run 'units -c' after making changes to any units data file.

       If you want to add your own units in addition to or in place of standard or site-wide sup-
       plemental units data files, you can include them in the '.units' file in your home  direc-
       tory.  If this file exists it is read after the standard units data file, so that any def-
       initions in this file will replace definitions of the same units in the standard data file
       or in files included from the standard data file.  This file will not be read if any units
       files are specified on the command line.  (Under Windows the personal units file is  named
       'unitdef.units'.)

       The  'units' program first tries to determine your home directory from the 'HOME' environ-
       ment variable.  On systems running Microsoft Windows, if 'HOME' does  not  exist,  'units'
       attempts  to find your home directory from 'HOMEDRIVE' and 'HOMEPATH'.  Running 'units -V'
       will display the location and name of your personal units file.

       You can specify an arbitrary file as your personal units data file with the  'MYUNITSFILE'
       environment  variable;  if  this variable exists, its value is used without searching your
       home directory.

   Defining New Units and Prefixes
       A unit is specified on a single line by giving its  name  and  an  equivalence.	 Comments
       start  with a '#' character, which can appear anywhere in a line.  The backslash character
       ('\') acts as a continuation character if it appears as the last character on a line, mak-
       ing  it	possible  to spread definitions out over several lines if desired.  A file can be
       included by giving the command '!include' followed by the file's name.  The '!'	 must  be
       the  first  character  on  the line.  The file will be sought in the same directory as the
       parent file unless you give a full path.  The name of the file to be included cannot  con-
       tain the comment character '#'.

       Unit  names  must not contain any of the operator characters '+', '-', '*', '/', '|', '^',
       ';', '~', the comment character '#', or parentheses.  They cannot begin	or  end  with  an
       underscore  ('_'),  a  comma  (',')  or	a decimal point ('.').	Names cannot begin with a
       digit, and if a name ends in a digit other than zero, the digit	must  be  preceded  by	a
       string  beginning  with	an  underscore, and afterwards consisting only of digits, decimal
       points, or commas.  For example, 'foo_2', 'foo_2,1', or 'foo_3.14' would  be  valid  names
       but 'foo2' or 'foo_a2' would be invalid.  You could define nitrous oxide as

	  N2O	  nitrogen 2  + oxygen

       but would need to define nitrogen dioxide as

	  NO_2	  nitrogen + oxygen 2

       Be careful to define new units in terms of old ones so that a reduction leads to the prim-
       itive units, which are marked with '!'  characters.  Dimensionless units are indicated  by
       using the string '!dimensionless' for the unit definition.

       When  adding  new units, be sure to use the '-c' option to check that the new units reduce
       properly.  If you create a loop in the units definitions,  then	'units'  will  hang  when
       invoked	with  the  '-c' option.  You will need to use the '--check-verbose' option, which
       prints out each unit as it is checked.  The program will still hang,  but  the  last  unit
       printed will be the unit that caused the infinite loop.

       If you define any units that contain '+' characters, carefully check them because the '-c'
       option will not catch non-conformable sums.  Be careful with the  '-'  operator	as  well.
       When  used  as a binary operator, the '-' character can perform addition or multiplication
       depending on the options used to invoke 'units'.  To ensure consistent  behavior  use  '-'
       only  as  a unary negation operator when writing units definitions.  To multiply two units
       leave a space or use the '*' operator with care, recalling that it has two possible prece-
       dence  values  and  may require parentheses to ensure consistent behavior.  To compute the
       difference of 'foo' and 'bar' write 'foo+(-bar)' or even 'foo+-bar'.

       Here is an example of a short data file that defines some basic units:

	  m	  !		  # The meter is a primitive unit
	  sec	  !		  # The second is a primitive unit
	  rad	  !dimensionless  # A dimensionless primitive unit
	  micro-  1e-6		  # Define a prefix
	  minute  60 sec	  # A minute is 60 seconds
	  hour	  60 min	  # An hour is 60 minutes
	  inch	  0.0254 m	  # Inch defined in terms of meters
	  ft	  12 inches	  # The foot defined in terms of inches
	  mile	  5280 ft	  # And the mile

       A unit that ends with a '-' character is a prefix.  If a prefix	definition  contains  any
       '/' characters, be sure they are protected by parentheses.  If you define 'half- 1/2' then
       'halfmeter' would be equivalent to '1 / (2 meter)'.

   Defining Nonlinear Units
       Some unit conversions of interest are  nonlinear;  for  example,  temperature  conversions
       between	the Fahrenheit and Celsius scales cannot be done by simply multiplying by conver-
       sion factors.

       When you give a linear unit definition such as 'inch 2.54 cm' you are  providing  informa-
       tion  that  'units'  uses to convert values in inches into primitive units of meters.  For
       nonlinear units, you give a functional definition that provides the same information.

       Nonlinear units are represented using a functional notation.  It is best  to  regard  this
       notation  not  as  a function call but as a way of adding units to a number, much the same
       way that writing a linear unit name after a number adds units to that number.  Internally,
       nonlinear  units  are defined by a pair of functions that convert to and from linear units
       in the data file, so that an eventual conversion to primitive units is possible.

       Here is an example nonlinear unit definition:

	  tempF(x) units=[1;K] (x+(-32)) degF + stdtemp ; \
			       (tempF+(-stdtemp))/degF + 32

       A nonlinear unit definition comprises a unit name, a dummy parameter name, two  functions,
       and  two  corresponding	units.	The functions tell 'units' how to convert to and from the
       new unit.  In order to produce valid results, the arguments of  these  functions  need  to
       have  the  correct  dimensions.	To facilitate error checking, you may optionally indicate
       units for these arguments.

       The definition begins with the unit name followed immediately (with no spaces)  by  a  '('
       character.   In	parentheses is the name of the parameter.  Next is an optional specifica-
       tion of the units required by the functions in this definition.	In the example above, the
       'tempF'	function  requires  an input argument conformable with '1'.  For normal nonlinear
       units definitions the forward function will always take	a  dimensionless  argument.   The
       inverse	function requires an input argument conformable with 'K'.  In general the inverse
       function will need units that match the quantity measured by  your  nonlinear  unit.   The
       purpose of the expression in brackets to enable 'units' to perform error checking on func-
       tion arguments, and also to assign units to range and  domain  specifications,  which  are
       described later.

       Next  the  function  definitions  appear.   In  the example above, the 'tempF' function is
       defined by

	  tempF(x) = (x+(-32)) degF + stdtemp

       This gives a rule for converting 'x' in the units 'tempF' to linear units of absolute tem-
       perature, which makes it possible to convert from tempF to other units.

       In  order to make conversions to Fahrenheit possible, you must give a rule for the inverse
       conversions. The inverse will be 'x(tempF)' and its definition appears after a ';' charac-
       ter.  In our example, the inverse is

	  x(tempF) = (tempF+(-stdtemp))/degF + 32

       This  inverse  definition takes an absolute temperature as its argument and converts it to
       the Fahrenheit temperature.  The inverse can be omitted by leaving out the ';'  character,
       but  then  conversions to the unit will be impossible.  If the inverse is omitted then the
       '--check' option will display a warning.  It is up to  you  to  calculate  and  enter  the
       correct	inverse  function  to  obtain proper conversions.  The '--check' option tests the
       inverse at one point and prints an error if it is not valid there, but this is not a guar-
       antee that your inverse is correct.

       If  you	wish to make synonyms for nonlinear units, you still need to define both the for-
       ward and inverse functions.  Inverse functions can be obtained using the '~' operator.  So
       to create a synonym for 'tempF' you could write

	  fahrenheit(x) units=[1;K] tempF(x); ~tempF(fahrenheit)

       You may define a function whose range and domain do not cover all of the real numbers.  In
       this case 'units' can handle errors better if you specify an appropriate range and domain.
       You specify the range and domain as shown below.

	  baume(d) units=[1;g/cm^3] domain=[0,130.5] range=[1,10] \
		   (145/(145-d)) g/cm^3 ; (baume+-g/cm^3) 145 / baume

       In  this  example  the domain is specified after the 'domain=' with the endpoints given in
       brackets.  One of the end points can be omitted to get an interval that goes to	infinity.
       So  the	range  could be specified as nonnegative by writing 'range=[0,]'.  Both the range
       and domain are optional and can appear independently and  in  any  order  along	with  the
       'units' specification.  The values in the range and domain are attached to the units given
       in the 'units' specification.  If you don't specify the units then  the	parameter  inputs
       are  reduced  to  primitive units for the numeric comparison to the values you give in the
       range or domain.  In this case you should only use 'range' or 'domain'  if  the	endpoints
       are zero and infinity.

       Specifying  the	range and domain allows 'units' to perform better error checking and give
       more helpful error messages when you invoke nonlinear units conversions outside	of  their
       bounds.	 It  also  enables  the  '-c' option to find a point in the domain to use for its
       point check of your inverse definition.

       You may occasionally wish to define a function that operates on units.  This can  be  done
       using  a nonlinear unit definition.  For example, the definition below provides conversion
       between radius and the area of a circle.  This definition requires a length as  input  and
       produces  an  area  as output, as indicated by the 'units=' specification.  Specifying the
       range as the nonnegative numbers can prevent cryptic error messages.

	  circlearea(r) units=[m;m^2] range=[0,]   pi r^2 ; sqrt(circlearea/pi)

       Sometimes you may be interested in a piecewise linear  unit  such  as  many  wire  gauges.
       Piecewise  linear units can be defined by specifying conversions to linear units on a list
       of points.  Conversion at other points will be done by linear  interpolation.   A  partial
       definition of zinc gauge is

	  zincgauge[in] 1 0.002, 10 0.02, 15 0.04, 19 0.06, 23 0.1

       In  this example, 'zincgauge' is the name of the piecewise linear unit.	The definition of
       such a unit is indicated by the embedded '[' character.	After  the  bracket,  you  should
       indicate  the  units  to  be  attached  to the numbers in the table.  No spaces can appear
       before the ']' character, so a definition like 'foo[kg meters]' is illegal; instead  write
       'foo[kg*meters]'.  The definition of the unit consists of a list of pairs optionally sepa-
       rated by commas.  This list defines a function for converting from  the	piecewise  linear
       unit  to  linear  units.  The first item in each pair is the function argument; the second
       item is the value of the function at that argument (in the units specified  in  brackets).
       In this example, we define 'zincgauge' at five points.  For example, we set 'zincgauge(1)'
       equal to '0.002 in'.  Definitions like this may be  more readable  if written using   con-
       tinuation characters as

	  zincgauge[in] \
	       1 0.002	\
	      10 0.02	\
	      15 0.04	\
	      19 0.06	\
	      23 0.1

       With the preceding definition, the following conversion can be performed:

	  You have: zincgauge(10)
	  You want: in
	      * 0.02
	      / 50
	  You have: .01 inch
	  You want: zincgauge
	      5

       If  you	define	a  piecewise linear unit that is not strictly monotonic, then the inverse
       will not be well defined.  If the inverse is requested  for  such  a  unit,  'units'  will
       return the smallest inverse.  The '--check' option will print a warning if a non-monotonic
       piecewise linear unit is encountered.

   Defining Unit List Aliases
       Unit list aliases are treated differently from unit definitions, because they are  a  data
       entry  shorthand  rather than a true definition for a new unit.	A unit list alias defini-
       tion begins with '!unitlist' and includes the alias and the definition;	for example,  the
       aliases included in the standard units data file are

	  !unitlist   hms     hr;min;sec
	  !unitlist   time    year;day;hr;min;sec
	  !unitlist   dms     deg;arcmin;arcsec
	  !unitlist   ftin    ft;in;1|8 in
	  !unitlist   usvol   cup;3|4 cup;2|3 cup;1|2 cup;1|3 cup;1|4 cup;\
			      tbsp;tsp;1|2 tsp;1|4 tsp;1|8 tsp

       Unit  list  aliases  are  only for unit lists, so the definition must include a ';'.  Unit
       list aliases can never be combined with units or other unit list aliases, so  the  defini-
       tion  of 'time' shown above could not have been shortened to 'year;day;hms'.  As usual, be
       sure to run 'units --check' to ensure that the units listed in unit list aliases are  con-
       formable.

NUMERIC OUTPUT FORMAT
       By  default,  results  of  conversions are shown to eight significant figures; this can be
       changed with the '--exponential' and '--output-format' options.	The former sets an  expo-
       nential	format	(i.e.,	scientific  notation) like that used in the original Unix 'units'
       program; the latter allows the format to be given as that of the printf	function  in  the
       ANSI C standard.

       The  format recognized with the '--output-format' option is a subset of that for printf().
       Only a floating-point format of the form '%'[flag][width]['.'precision]type is allowed: it
       must  begin  with  '%',	and must end with a floating-point type specifier ('E' or 'e' for
       scientific notation, 'f' for fixed-point decimal, or 'G' or 'g' to specify the  number  of
       significant  figures).	The format specification may include one optional flag ('+', '-',
       '#', or a space), followed by an optional value	for  the  minimum  field  width,  and  an
       optional  precision  specification that begins with a period (e.g., '.6').  In addition to
       the digits, the field width includes the decimal point, the exponent, and the sign if  any
       of  these  are shown.  A width specification is typically used with fixed-point decimal to
       have columns of numbers align at the  decimal  point;  it  normally  is	not  useful  with
       'units'.  Non-floating-point type specifiers make no sense for 'units', and are forbidden.

       The  default  format  is '%.8g'; for greater precision, you could specify '-o %.15g'.  The
       'G' and 'g' formats use exponential format whenever the exponent would be less than -5, so
       the  value  0.000013 displays as '1.3e-005'.  If you prefer fixed-point display, you might
       specify '-o %.8f'; however, very small numbers may display very few  significant  figures,
       and for very small numbers, may show nothing but zeros.

       See the documentation for printf() for more detailed descriptions of the format specifica-
       tion.

LOCALIZATION
       Some units have different values in different locations.  The localization feature  accom-
       modates	this  by  allowing  a  units  data file to specify definitions that depend on the
       user's locale.

   Locale
       A locale is a subset of a user's environment that indicates the user's language and  coun-
       try, and some attendant preferences, such as the formatting of dates.  The 'units' program
       attempts to determine the locale from the POSIX setlocale  function;  if  this  cannot  be
       done, 'units' examines the environment variables 'LC_CTYPE' and 'LANG'.	On POSIX systems,
       a locale is of the form language'_'country, where language is the two-character code  from
       ISO  639-1  and	country is the two-character code from ISO 3166-1; language is lower case
       and country is upper case. For example,	the  POSIX  locale  for  the  United  Kingdom  is
       'en_GB'.

       On  systems running Microsoft Windows, the value returned by setlocale() is different from
       that on POSIX systems; 'units' attempts to map the Windows value to a POSIX value by means
       of   a	table	in   the   file   'locale.map'	 in   the   same   directory,	typically
       '/usr/local/share/units', as the default units data files.  The file includes entries  for
       many  combinations  of language and country, and can be extended to include other combina-
       tions.  The 'locale.map' comprises two tab-separated columns; each entry is of the form

	  Windows-locale   POSIX-locale

       where POSIX-locale is as described above, and Windows-locale typically spells out both the
       language and country.  For example, the entry for the United States is

	  English_United States   en_US

       You can force 'units' to run in a desired locale by using the '-l' option.

       In  order  to create unit definitions for a particular locale you begin a block of defini-
       tions in a unit datafile with '!locale' followed by a locale name.  The '!'  must  be  the
       first  character on the line.  The 'units' program reads the following definitions only if
       the current locale matches.  You end the block of localized units with '!endlocale'.  Here
       is an example, which defines the British gallon.

	  !locale en_GB
	  gallon       4.54609 liter
	  !endlocale

   Additional Localization
       Sometimes  the  locale  isn't  sufficient  to  determine unit preferences.  There could be
       regional preferences, or a company  could  have	specific  preferences.	 Though  probably
       uncommon,  such differences could arise with the choice of English customary units outside
       of English-speaking countries.  To address this,  'units'  allows  specifying  definitions
       that  depend on environment variable settings.  The environment variables can be controled
       based on the current locale, or the user can set them to force a particular group of defi-
       nitions.

       A  conditional  block  of  definitions  in  a units data file begins with either '!var' or
       '!varnot' following by an environment variable name and then a  space  separated  list  of
       values.	 The  leading  '!'  must appear in the first column of a units data file, and the
       conditional block is terminated by '!endvar'.  Definitions in blocks beginning with '!var'
       are  executed  only if the environment variable is exactly equal to one of the listed val-
       ues.  Definitions in blocks beginning with '!varnot' are executed only if the  environment
       variable does not equal any of the list values.

       The  inch has long been a customary measure of length in many places.  The word comes from
       the latin uncia meaning ``one twelfth,'' referring to its relationship with the foot.   By
       the  20th  century, the inch was officially defined in English-speaking countries relative
       to the yard, but until 1959, the yard differed slightly among those countries.  In  France
       the customary inch, which was displaced in 1799 by the meter, had a different length based
       on a french foot.  These customary definitions could be accomodated as follows:

	  !var INCH_UNIT usa
	  yard		3600|3937 m
	  !endvar
	  !var INCH_UNIT canada
	  yard		0.9144 meter
	  !endvar
	  !var INCH_UNIT uk
	  yard		0.91439841 meter
	  !endvar
	  !var INCH_UNIT canada uk usa
	  foot		1|3 yard
	  inch		1|12 foot
	  !endvar
	  !var INCH_UNIT france
	  foot		144|443.296 m
	  inch		1|12 foot
	  line		1|12 inch
	  !endvar
	  !varnot INCH_UNIT usa uk france canada
	  !message Unknown value for INCH_UNIT
	  !endvar

       When  'units'  reads  the  above  definitions  it  will	check  the  environment  variable
       'INCH_UNIT'  and load only the definitions for the appropriate section.	If 'INCH_UNIT' is
       unset or is not set to one of the four values listed then 'units' will run the last block.
       In  this case that block uses the '!message' command to display a warning message.  Alter-
       natively that block could set default values.

       In order to create default values that are overridden by user settings the data	file  can
       use  the '!set' command, which sets an environment variable only if it is not already set;
       these settings are only for the current 'units' invocation and do not persist.  So if  the
       example	above  were preceded by '!set INCH_UNIT france' then this would make 'france' the
       default value for 'INCH_UNIT'.  If the user had set the variable in the environment before
       invoking 'units', then 'units' would use the user's value.

       To  link  these	settings  to  the  user's  locale you combine the '!set' command with the
       '!locale' command.  If you wanted to combine the above example with suitable  locales  you
       could do by preceding the above definition with the following:

	  !locale en_US
	  !set INCH_UNIT usa
	  !endlocale
	  !locale en_GB
	  !set INCH_UNIT uk
	  !endlocale
	  !locale en_CA
	  !set INCH_UNIT canada
	  !endlocale
	  !locale fr_FR
	  !set INCH_UNIT france
	  !endlocale
	  !set INCH_UNIT france

       These definitions set the overall default for 'INCH_UNIT' to 'france' and set default val-
       ues for four locales appropriately.  The overall default setting comes  last  so  that  it
       only applies when 'INCH_UNIT' was not set by one of the other commands or by the user.

       If  the variable given after '!var' or '!varnot' is undefined then 'units' prints an error
       message and ignores the definitions that follow.  Use '!set' to create defaults to prevent
       this  situation from arising.  The '-c' option only checks the definitions that are active
       for the current environment and locale, so when adding new definitions take care to  check
       that all cases give rise to a well defined set of definitions.

ENVIRONMENT VARIABLES
       The 'units' program uses the following environment variables:

       HOME   Specifies the location of your home directory; it is used by 'units' to find a per-
	      sonal units data file '.units'.  On  systems  running  Microsoft	Windows,  'units'
	      tries to determine your home directory from the 'HOMEDRIVE' and 'HOMEPATH' environ-
	      ment variables if 'HOME' does not exist.

       LC_CTYPE, LANG
	      Checked to determine the locale if 'units' cannot obtain it from the operating sys-
	      tem.  Sections of the standard units data file are specific to certain locales.

       MYUNITSFILE
	      Specifies your personal units data file.	If this variable exists, 'units' uses its
	      value rather than searching your home directory for '.units'.  The  personal  units
	      file will not be loaded if any data files are given using the '-f' option.

       PAGER  Specifies  the pager to use for help and for displaying the conformable units.  The
	      help function browses the units database and calls the pager using the '+n'n syntax
	      for  specifying a line number.  The default pager is 'more'; 'PAGER' can be used to
	      specify alternatives such as 'less', 'pg', 'emacs', or 'vi'.

       UNITS_ENGLISH
	      Set to either 'US' or 'GB' to choose United States or British  volume  definitions,
	      overriding the default from your locale.

       UNITSFILE
	      Specifies  the units data file to use (instead of the default).  You can only spec-
	      ify a single units data file using this environment variable.  If units data  files
	      are  given  using the '-f' option, the file specified by 'UNITSFILE' will be not be
	      loaded unless the '-f' option is given with the empty string ('units -f ""').

UNICODE SUPPORT
       The standard units data file is written in Unicode using the UTF-8 encoding.  Portions  of
       the  file  that are not plain ASCII begin with '!utf8' and end with '!endutf8'.	As usual,
       the '!'	must appear as the first character on the line.  If a line of a  data  file  con-
       tains byte sequences that are invalid UTF-8 or non-printing UTF-8 then 'units' ignores the
       entire line.

       When 'units' runs it checks the locale to  determine  the  character  set.   If	UTF-8  is
       listed,	then  'units'  reads the utf8 definitions.  If any other character set is in use,
       then 'units' works in plain ASCII without support for extended characters.

READLINE SUPPORT
       If the 'readline' package has been compiled in, then when 'units' is  used  interactively,
       numerous command line editing features are available.  To check if your version of 'units'
       includes 'readline', invoke the program with the '--version' option.

       For complete information about 'readline', consult the documentation  for  the  'readline'
       package.  Without any configuration, 'units' will allow editing in the style of emacs.  Of
       particular use with 'units' are the completion commands.

       If you type a few characters and then hit ESC followed by '?'  then 'units' will display a
       list  of  all  the  units  that start with the characters typed.  For example, if you type
       'metr' and then request completion, you will see something like this:

	  You have: metr
	  metre 	    metriccup	      metrichorsepower	metrictenth
	  metretes	    metricfifth       metricounce	metricton
	  metriccarat	    metricgrain       metricquart	metricyarncount
	  You have: metr

       If there is a unique way to complete a unitname, you can hit the TAB key and 'units'  will
       provide	the  rest  of  the unit name.  If 'units' beeps, it means that there is no unique
       completion.  Pressing the TAB key a second time will print the list of all completions.

UPDATING CURRENCY EXCHANGE RATES
       The units program includes currency exchange rates and prices for some precious metals  in
       the  database.	Of  course,  these  values  change over time, sometimes very rapidly, and
       'units'	cannot	provide  real  time  values.   To  update  the	exchange  rates  run  the
       'units_cur',   which   rewrites	 the  files  containing  the  currency	rates,	typically
       '/usr/local/share/units/currency.units'.  This program must be run with	suitable  permis-
       sions  to  write  the file.  To keep the rates updated automatically, it could be run by a
       cron job on a Unix-like system, or a similar scheduling program	on  a  different  system.
       Currency  exchange rates are taken from Time Genie (http://www.timegenie.com) and precious
       metals pricing from Packetizer (www.packetizer.com).  These sites update once per day,  so
       there  is  no  benefit  in  running  the update script more often than daily.  You can run
       'units_cur' with a filename specified on the command line and it will write  the  data  to
       that file.  If you give '-' for the file it will write to standard output.

DATABASE COMMAND SYNTAX
       unit definition
	      Define a regular unit.

       prefix- definition
	      Define a prefix.

       funcname(var)  units=[in-units,out-units]  domain=[x1,x2]  range=[y1,y2] definition(var) ;
       inverse(funcname)
	      Define a nonlinear unit or unit function.  The three  optional  keywords	'units=',
	      'range='	and  'domain=' can appear in any order.  The definition of the inverse is
	      optional.

       tabname[out-units] pair-list
	      Define a piecewise linear unit.  The pair list gives the points on the table listed
	      in ascending order.

       !endlocale
	      End a block of definitions beginning with '!locale'

       !endutf8
	      End a block of definitions begun with '!utf8'

       !endvar
	      End a block of definitions begun with '!var' or '!varnot'

       !include file
	      Include the specified file.

       !locale value
	      Load the following definitions only of the locale is set to value.

       !message text
	      Display text when the database is read unless the quiet option ('-q') is enabled.

       !set variable value
	      Sets  the  environment variable, variable, to the specified value only if it is not
	      already set.

       !unitlist alias definition
	      Define a unit list alias.

       !utf8  Load the following definitions only if 'units' is running with UTF-8 enabled.

       !var variable value-list
	      Load the following definitions only if the environment variable, variable is set to
	      one  of the values listed on the space separated value list. If variable is not set
	      then 'units' prints an error message and ignores the following definitions.

       !varnot variable value-list
	      Load the following definitions only if the environment variable,	variable  is  not
	      set  to one of the values listed on the space separated value list.  If variable is
	      not set then 'units' prints an error message and ignores the following definitions.

GNU FREE DOCUMENTATION LICENSE
FILES
       /usr/share/units/definitions.units -- the standard units data file

AUTHO
					  27 April 2012 				 UNITS(1)
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