Python script for surveying how often different directories produce the same ftok() value

find_ftok_collisions.py

import argparse
import os
from collections import defaultdict

def ftok(fn, proj_id):
    st = os.stat(fn)
    return (st.st_ino & 0xffff) | ((st.st_dev & 0xff) << 16) | ((proj_id & 0xff) << 24)

parser = argparse.ArgumentParser()
parser.add_argument('top_dir')
args = parser.parse_args()

ftok_value_to_fns = defaultdict(list)

proj_id = 23 # SHM_projectID from STAR Genome.cpp
for dirpath, *rest in os.walk(args.top_dir):
    ftok_value = ftok(dirpath, proj_id)
    ftok_value_to_fns[ftok_value].append(dirpath)

for ftok_value, fns in ftok_value_to_fns.items():
    if len(fns) > 1:
        print(f'{ftok_value}:')
        for fn in fns:
            print(f'\t{fn}')