How to find words from one file in another file?

Question

In one text file, I have 150 words. I have another text file, which has about 100,000 lines.

How can I check for each of the words belonging to the first file wh

Answer 1

You can use grep -f:

grep -Ff "first-file" "second-file"

OR else to match full words:

grep -w -Ff "first-file" "second-file"

UPDATE: As per the comments:

awk 'FNR==NR{a[$1]; next} ($1 in a){delete a[$1]; print $1}' file1 file2