8 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 primitive 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 definitions active in the current locale are checked. You should always run units with this option after modifying a units data file.

--check-verbose

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 scientific 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 precision, you could specify ‘-o %.15g’. See Numeric Output Format, and the documentation 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 personal 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 behavior.

-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 multiplier 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.