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
If you type
units "2 liters" quarts
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 will print a message giving the reduced form of
each unit and it will return failure (nonzero) to the calling environment.
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.