How to run grep inside awk?

Question

Suppose I have a file input.txt with few columns and few rows, the first column is the key, and a directory dir with files which contain some of these

Answer 1

grep requires parameters in order: [what to search] [where to search]. You need to merge keys received from awk and pass them to grep using the \| regexp operator. For example:

arturcz@szczaw:/tmp/s$ cat words.txt 
foo
bar
fubar
foobaz
arturcz@szczaw:/tmp/s$ grep 'foo\|baz' words.txt 
foo
foobaz

Finally, you will finish with:

grep `commands|to|prepare|a|keywords|list` directory