If you're not happy with the output of tractstats2table and want something custom, you can just do a search in the stats files. They're simple text files. You can see how these files are named and what their contents look like here:
https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/TraculaStatistics#Anisotropyanddiffusivityaveragedoveranentirepathway

You'd have to search for the lines that contain subjectname, pathwayname, and the name of the diffusion measure that you want.
From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of Zeng, Qi <qi.zeng@icahn.mssm.edu>
Sent: Friday, May 8, 2020 9:58 AM
To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] tracula stats summary
 

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Hi, 

Is it possible to collect all 18 tracts stats into a single file?
Has tried:
"tractstats2table --load-pathstats-from-file paths.txt --overall --tablefile tractAll.txt"
Path.txt contains all the subjects' 18 paths' full path directory
Error message:
"all stats files need to have the same pathwayname. try verbose option
These are the pathwaynames found: ['fmajor', 'fminor', 'lh.atr', 'lh.cab', 'lh.ccg', 'lh.cst', 'lh.ilf', 'lh.slfp', 'lh.slft', 'lh.unc', 'rh.atr', 'rh.cab', 'rh.ccg', 'rh.cst', 'rh.ilf', 'rh.slfp', 'rh.slft', 'rh.unc']"

Best, 
Qi

--

Ph.D. candidate 
Icahn School of Medicine at Mount Sinai