CAD tip # 10138:

You can choose whether the resulting length will be annotated with a true linear dimension or with a curved "dimension" copying the shape of the dimensioned object. The annotation text format (prefixed with ">>" by default) can be customized.

Besides the total length you can also dimension the distance (along the curve) of two picked points on the curve (the option betweenPoints). The dimension is created in the layer "Dimensions", or in the layer of the dimensioned curve entity (the option Entlayer).

You can download the DimCurve add-on utility from Download, load it with APPLOAD and run it by typing the DimCurve command.

Sample video:

The default text formatting function (prefix "»", number of decimal places by DIMDEC) can be redefined by using/defining your own function _DimCurveFormat.

  
(defun _DimCurveFormat (n)  
 (strcat "\U+00BB " (rtos n (getvar "lunits")(getvar "dimdec")))  
)