I met an error when I try to run mris_preproc. Actually i succeeded this command with my own scripts and fsgd files before. 

There are 2groups with one covariates but I keep getting this error like below. 

mris_preproc --fsgd TESTTEST_age_only.fsgd --hemi lh --meas thickness --target fsaverage --fwhm fwhm10 --o lh.thickness_age.s10.mgh
ERROR: no subjects specified

I attached my fsgd file. 

This fsgd file was made using emacs. 

Regards, 

Hyon-Ah Yi.