you simply want to pick 6 random lines and change them?

not 6random lines
read everyall lines and there is 1.txt 2.txt 3.txt 4.txt 5.txt 6.txt 7.txt 8.txt 9.txt ~~ 22.txt 23.txt 24.txt 25.txt file in every directories
namely about 25 files exist
and i want to randomly select 6 files among 25 files
and rename selected 6 text files as words1.word words2.word words3.word words4.word words5.word words6.word .