afni.nimh.nih.gov

If you want to find the number of nodes in a surface, you can use :

SurfInfo -N_Node -spec my.spec -surf_A surfname
N_Node=198812

where "my.spec" would be the name of the spec file you are interested in, and surfname is the name of the surface (like pial, wm, smoothwm,...).

If you want to find the number of nodes listed in a niml.dset or functional gifti dataset file, you can use:

3dinfo -ni ~/schaefer_yeo/MNI_N27/my.niml.dset
198812