3 Using 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 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 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.

units does not require a space between a numerical value and the unit, so the previous example can be given as

units 2liters quarts

to avoid having to quote the first argument.

If the conversion is successful, units will return success (zero) to the calling environment. If you enter non-conformable units, then units will print a message giving the reduced form of each unit and it will return failure (nonzero) to the calling environment.

If the --conformable option is given, only one unit expression is allowed, and units will print all units conformable with that expression; it is equivalent to giving ? at the ‘You want:’ prompt. For example,

units --conformable gauss
B_FIELD   tesla
Gs        gauss
T         tesla
gauss     abvolt sec / cm^2
stT       stattesla
statT     stattesla
stattesla statWb/cm^2
tesla     Wb/m^2

If you give more than one unit expression with the --conformable option, the program will exit with an error message and return failure. This option has no effect in interactive mode.

If the --terse (-t) option is given with the --conformable option, conformable units are shown without definitions; with the previous example, this would give

units --terse --conformable gauss
B_FIELD
Gs
T
gauss
stT
statT
stattesla
tesla

When the --conformable option is not given and you invoke units with only one argument, units will print the definition of the specified unit. It will return failure if the unit is not defined and success if the unit is defined.