export geometric stiffness matrix in abaqus software
Abaqus doesn't output stiffness matrices.  If you already know Abaqus and only want to do buckling, you might want to try CalculiX. I think it can output a stiffness matrix and uses Abaqus-style input files.
I need export geometric(stress or diffrential) stiffness matrix in linear buckling problem at abaqus software for use in matlab program, i find method export  of usual stiffness matrix, but i cant find any data about export geometric stiffness matrix in abaqus script, 
Can some one help me about it?
for example when i export stiffness matrix in buckling problem,the result is same as stiffness matrix in linear static problem