UNIX for Dummies Questions & Answers

I couldn't find the original thread that I created and since I didn't get a definitive answer, I figured I'd try again. Maybe this time I can describe what I want a little better.


I've got two files, each with thousands of names all separated by new line. I want to know if 'name in file1' also appears anywhere in file 2 then print it out for me (though output isn't the problem).

I've thought that maybe there's a way to walk through the first file and with each line then walk through each line in the second file (something like a nested loop statement) and then go from there. I'm just wondering if that will work of if there is a better and EASIER way.

Thanks

Use associative arrays in awk. This finds names that occur in both files. It is case-sensitive and sensitive to extra spaces - in other words an exact match

Code:

awl '{ if(FILENAME=="file1") (arr[$0]++}
        if(FILENAME=="file2") {if($0 in arr) {print $0)} }
      }'  file1 file2

Nested loops like you describe take far too long. This is about as godd as it gets.

Hi, have You tried this?

Something like:

Code:

while read name;do grep "$name" file2;done < file1

And You could do something like:

Code:

while read name;do echo $name:;grep "$name" file2;done < file1

Or some other action based on return value of grep?

Code:

while read name;do ;grep -q "$name" file2 && echo $name found in file2;done < file1

And it would help if You could show the source of the file, if this doesn't work. Have You considered sorting the files and using diff?

Best regards
/Lakris