Shell Programming and Scripting

Hello,

I'm interested in finding all occurrences of the terms in file1 in file2, which are both csv files. I can do this with a loop but I'm interested in knowing if I can also do it with the help of xargs and grep. What I have tried:

Code:

cat file1 | xargs grep file2

The problem is that grep tries to open the terms in file1 instead of using them as patterns.

Code:

grep -F file1 file2

Code:

fgrep file1 file2

Thank you, that is so much better! I managed to get grep -f to do what I wanted, was not aware of this.

If you want to search for the patterns from a file ( file1 in your example ) , you must use the "-f" option.

"grep -F" is equivalent to "fgrep" ( treating patterns as fix string and not regex) but differ from "grep -f" (patterns from file ) . you probably want to combine the both.

Code:

grep -F -f file1 file2

or

Code:

fgrep -f file1 file2

Thank you, I used the "-f" option, adding "-F" as well made it significantly faster.

---------- Post updated 10-12-11 at 12:27 AM ---------- Previous update was 10-11-11 at 04:43 AM ----------

I have another question related to this use of grep. If I instead wan to list all items in file1 that does not exist in file2 by negating how can that be done?

I tried the -v flag but it did not do this, am I missing something here or is it not possible to do this with grep alone? I have used -v before with grep but never combined with -f that is new to me.

Code:

grep -v -F -f file1 file2

EDIT:
I managed to get this working with the following script, any comments or tips if there are easier ways to accomplish the same this would be appreciated.

Code:

#!/bin/bash

if [ "$#" -ne 2 ]
then
    echo "Missing arguments"
    exit 1
fi

while read line ; do RESULT=$(grep "$line" "$1") ;

if [ -z "$RESULT" ]
then
     echo "$line"
fi ; done < "$2"

Code:

grep -vFf file2 file1

That still does not work I'm afraid.

file1 contains 99 lines which all appear in file2.

file2 contains 109 lines.

What I want is to get the 10 lines that does not appear in file1.

Doing this:

Code:

grep -vFf file1 file2 | wc -l

gives me: 109

but switching the order gives me: 0