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 units expression, and type the new units you want.
You will probably need to protect the units expressions from
interpretation by the shell using single 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 (0)
to the calling environment. If units is given non-conformable
units to convert, it will print a message giving the reduced form of
each unit and it will return failure (nonzero) to the calling environment.
When units is invoked 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.