units1

Usage

Overview

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 arguments 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 statistics 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. Otherwise, print an error message.

-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 command line. The program will not print prompts. It will print out the result of the single specified conversion. Both arguments, 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”)

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 gigabytes 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 numbers (“|”) 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 illustrated 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