find lines from one file in another

Question

So I have a file1.txt with a list of names, and a file2.txt with another list of names and I need a list with the names that are in both files.

I tried grep-f file1.txt file2.txt > newlist.txt but for some reason it isn't working, and the newlist.txt has names that are not in file1.

Does anyone know why this is happening and what i could do to get only the names that are on both lists?

thank you.

Answer 1

If file1.txt and file2.txt are sorted, you could use 'comm'

comm -12 file1.txt file2.txt > newlist.txt

Answer 2

Your grep -f file1.txt file2.txt > newlist.txt is a nice thought, but will give too much hits when file1.txt has "s10" and file2.txt has "slass100". You want to match the complete line, so try

grep -Fxf file1.txt file2.txt > newlist.txt

This should be faster than a solution that requires sorting first.