Prior to issuing a solve command, redirect output to a text file, like this:
/output,outputfile_name,out
when your model has solved, redirect output (back to the screen for example)
/output
This is much easier if you have a command file i.e.
/prep7
model creation commands...
...
...
...
/solu
boundary conditions...
...
...
...
save
/output,outputfile,out
solve
fini
/output
All of your modal mass participation factors etc. will appear in this output file.
Cheers,
-- drej --