Dear Freesurfers:
mri_surf2surf 
‐‐hemi 
lh
 ‐‐s 
fsaverage
 ‐‐sval
 att-lh-thickness.mgh
 ‐‐fwhm 
10 
‐‐tval
 att-lh-thickness.10.mgh
I got error
" command not found"
or 
"ERROR: Option 
‐‐hemi unknown"

although I can do mri_surf2surf 
‐‐help with not problem

I checked  fsaverage, OK 
but my 
att-lh-thickness.mgh is not inside the fsaverage folder
the result of unix  "ls" command is

att-lh-thickness.mgh
fsaverage

Is there a tutorial data so that I can go through group analysis step by step?
Thanks!