Write force <tt>F</tt> on all atoms into a text file with filename specified by <tt>finalcnfile</tt>.

<p>
Each line of the file contains <tt>i _F[i].x _F[i].y _F[i].z fixed[i]</tt>.

<p>
If <tt>input = 1</tt> is set before calling this command, then only atoms with <tt>fixed[i] == 1</tt>
have their information written into the file.  In this case, 
each line of the file contains <tt>i _F0[i].x _F0[i].y _F0[i].z fixed[i]</tt>.

