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UNITS(1)		FreeBSD	General	Commands Manual		      UNITS(1)

NAME
     units -- conversion calculator

SYNOPSIS
     units [-ehqtUVv] [-f unitsfile] [-o format] [from to]

DESCRIPTION
     The units program converts	quantities expressed in	various	scales to
     their equivalents in other	scales.	 It can	only handle multiplicative or
     affine scale changes.

     units can work interactively by prompting the user	for input (see
     EXAMPLES) or non-interactively, providing a conversion for	given argu-
     ments from	and to.

     The following options are available:

     -e, --exponential
	      Same as -o %6e (see the description of the -o flag).

     -f	unitsfile, --file unitsfile
	      Specify the name of the units data file to load.	This option
	      may be specified multiple	times.

     -H	historyfile, --history historyfile
	      Ignored, for compatibility with GNU units.

     -h, --help
	      Show an overview of options.

     -o	format,	--output-format	format
	      Select the output	format string by which numbers are printed.
	      Defaults to "%.8g".

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

     -t, --terse
	      Only print the result.  This is used when	calling	units from
	      other programs for easy to parse results.

     -U, --unitsfile
	      Print the	location of the	default	unit file if it	exists.	 Oth-
	      erwise, print "Units data	file not found".

     -V, --version
	      Print the	version	number (which is fixed at "FreeBSD units"),
	      the path to the units data file and exit.

     -v, --verbose
	      Print the	units in the conversion	output.	 Be more verbose in
	      general.

     from to  Allow a single unit conversion to	be done	directly from the com-
	      mand line.  The program will not print prompts.  It will print
	      out the result of	the single specified conversion.  Both argu-
	      ments, i.e., from	and to,	can be just a unit (e.g., "cm"), a
	      quantity (e.g., "42"), or	a quantity with	a unit (e.g., "42 cm")

   Mathematical	operators
     -	 Powers	of units can be	specified using	the "^"	character as shown in
	 the example, or by simple concatenation: "cm3"	is equivalent to
	 "cm^3".  See the BUGS section for details on the limitations of expo-
	 nent values.
     -	 Multiplication	of units can be	specified by using spaces (" "), a
	 dash ("-") or an asterisk ("*").
     -	 Division of units is indicated	by the slash ("/").
     -	 Division of numbers must be indicated using the vertical bar ("|").

     Note that multiplication has a higher precedence than division, so
     "m/s/s" is	the same as "m/s^2" or "m/s s".

   Units
     The conversion information	is read	from a units data file.	 The default
     file includes definitions for most	familiar units,	abbreviations and met-
     ric 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

     The unit "pound" is a unit	of mass.  Compound names are run together so
     "pound force" is a	unit of	force.	The unit "ounce" is also a unit	of
     mass.  The	fluid ounce is "floz".	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
     units will	try to remove a	trailing "s" or	a trailing "es"	and check
     again for a match.

   Units file format
     To	find out what units are	available read the standard units file.	 If
     you want to add your own units you	can supply your	own file.  A unit is
     specified on a single line	by giving its name and an equivalence.	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.	 Comments in the unit definition file begin
     with a "#"	or "/" character at the	beginning of a line.

     Prefixes are defined in the same way as standard units, but with a	trail-
     ing dash ("-") at the end of the prefix name.  If a unit is not found
     even after	removing trailing "s" or "es", then it will be checked against
     the list of prefixes.  Prefixes will be removed until a legal base	unit
     is	identified.

ENVIRONMENT
     PATH  The colon-separated list of root directories	at which units tries
	   to find /usr/share/misc/definitions.units.

	   For example if PATH is set to "/tmp:/:/usr/local", no -f flags are
	   provided, and /usr/share/misc/definitions.units is missing then
	   units tries to open the following files as the default units	file:
	   /tmp/usr/share/misc/definitions.units,
	   /usr/share/misc/definitions.units, and
	   /usr/local/usr/share/misc/definitions.units.

FILES
     /usr/share/misc/definitions.units	The standard units file.

EXIT STATUS
     The units utility exits 0 on success, and >0 if an	error occurs.

EXAMPLES
     Example 1:	Simple conversion of units

       This example shows how to do simple conversions,	for example from giga-
       bytes to	bytes:

	 $ units -o %0.f -t '4 gigabytes' bytes
	 4294967296

       The -o %0.f part	of the command is required to print the	result in a
       non-scientific notation (e.g, 4294967296	instead	of 4.29497e+09).

     Example 2:	Interactive usage

       Here is an example of an	interactive session where the user is prompted
       for units:

	 You have: meters
	 You want: feet
		 * 3.2808399
		 / 0.3048

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

	 You have: meters/s
	 You want: furlongs/fortnight
		 * 6012.8848
		 / 0.00016630952

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

	 You have: 85 degF
	 You want: degC
		 29.444444

     Example 3:	Difference between "|" and "/" division

       The following command shows how to convert half a meter to centimeters.

	 $ units '1|2 meter' cm
		 * 50
		 / 0.02

       units prints the	expected result	because	the division operator for num-
       bers ("|") was used.

       Using the division operator for units ("/") would result	in an error:

	 $ units '1/2 meter' cm
	 conformability	error
		 0.5 / m
		 0.01 m

       It is because units interprets "1/2 meter" as "0.5/meter", which	is not
       conformable to "cm".

     Example 4:	Simple units file
       Here is an example of a short units file	that defines some basic	units:

	 m	   !a!
	 sec	   !b!
	 micro-	   1e-6
	 minute	   60 sec
	 hour	   60 min
	 inch	   0.0254 m
	 ft	   12 inches
	 mile	   5280	ft

     Example 5:	Viewing	units and conversions of the default units file
       The following shell one-liner allows the	user to	view the contents of
       the default units file:

	 $ less	"$(units -U)"

DIAGNOSTICS
     can't find	units file '%s'	 The default units file	is not in its default
     location (see FILES) and it is not	present	in any file tree starting with
     their roots at directories	from PATH (see ENVIRONMENT).

     cap_rights_limit()	failed	See capsicum(4).

     conformability error  It is not possible to reduce	the given units	to one
     common unit: they are not conformable.  Instead of	a conversion, units
     will display the reduced form for each provided 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

     Could not initialize history  See editline(3).

     dupstr  strdup(3) failed.

     memory for	prefixes exceeded in line %d  Over 100 prefixes	were defined.

     memory for	units exceeded in line %d  Over	1000 prefixes were defined.

     memory overflow in	unit reduction	The requested conversion involves too
     many units	(see BUGS).

     redefinition of prefix '%s' on line %d ignored

     redefinition of unit '%s' on line %d ignored

     unexpected	end of prefix on line %d

     unexpected	end of unit on line %d

     Units data	file not found	The default units file is missing.

     unable to enter capability	mode  See capsicum(4).

     unable to open units file '%s'  One of the	user-specified units files
     cannot be opened.

     unit reduces to zero

     unknown unit '%s'	The provided unit cannot be found in the units file.

     WARNING: conversion of non-proportional quantities.  units	may fail to
     convert from to to	because	the units are not proportional.	 The warning
     is	printed	when a quantity	is a part of the to argument.  It can be il-
     lustrated on an example of	conversion from	Fahrenheit to Celsius:

       $ units "degF" "degC"
		(-> x*0.55555556g -17.777778g)
		(<- y*1.8g 32g)
       $ units "degF" "1 degC"
       WARNING:	conversion of non-proportional quantities.
		(-> x*0.55555556g -17.777778g)
		(<- y*1.8g 32g)
       $ units "1 degF"	"1 degC"
       WARNING:	conversion of non-proportional quantities.
	       -17.222222

SEE ALSO
     bc(1)

HISTORY
     The units first appeared in NetBSD	and was	ported to FreeBSD 2.2.0.

     The manual	page was significantly rewritten in FreeBSD 13.0 by Mateusz
     Piotrowski	<0mp@FreeBSD.org>.

AUTHORS
     Adrian Mariano <adrian@cam.cornell.edu>

BUGS
     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 does	not
     take so long to load the units list and check for duplication.

     It	is not possible	to convert a negative value.

     The units program does not	handle reductions of long lists	of units very
     well:

       $ units "$(yes m	| head -n 154)"	"$(yes cm | head -n 154)"
	       * 1e+308
	       / 1e-308
       $ units "$(yes m	| head -n 333)"	"$(yes cm | head -n 333)"
	       * inf
	       / 0
       $ units "$(yes m	| head -n 500)"	"$(yes cm | head -n 500)"
       units: memory overflow in unit reduction
       conformability error
	       1 m^500
	       1 centi cm^499
       $ units "$(yes m	| head -n 501)"	"$(yes cm | head -n 501)"
       units: memory overflow in unit reduction
       units: memory overflow in unit reduction
       units: memory overflow in unit reduction
       conformability error
	       1 m^500
	       1 centi cm^499

FreeBSD	13.0			March 17, 2020			  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | FILES | EXIT STATUS | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | BUGS

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