http://ngc891.blogdns.net/projects/formol/formol.html

Formol is a command-line molar weight calculator.

Just type on the command-line `formol' following by a chemical formula. You can use brackets, coefficients and any of the first 109 elements of the periodic table. See Documentation for more information on syntax.

Examples:

  $ formol CH3CH2OH

  46.069

  $ formol EtOH

  46.069

  $ formol Si[OEt]4

  208.33

  $ formol PhSi[OMe]3

  198.294  

Get the sourcecode here : http://sourceforge.net/projects/formol