Compare two files in linux?

Question

I have two files that i am trying to compare. File1.txt and File2.txt. File1.txt looks like :-

name1 12.12.365.237 name2 12.90.543.87 name3 34.47.26.230 name4 11.10.90.234 name5 10.11.12.15

Whereas my file2 looks like :-

10.11.12.15 12.12.365.237 11.10.90.234

I am trying to write a script to identify which IP addresses are in file1 which are not present in file2 and output the name and the IP in a separate file and convert it into CSV. so the desired output will be :-

name2 12.90.543.87 name3 34.47.26.230

I tried using grep like this :-

grep -Fxvf File2.txt File1.txt >> not-in-File2.txt mv not-in-File2.txt not-in-File2.csv

But the grep command doesn't seem to be working as it gives the wrong output.It currently gives me the entire file1 as it is.

name1 12.12.365.237 name2 12.90.543.87 name3 34.47.26.230 name4 11.10.90.234 name5 10.11.12.15

What would be the best way to compare these 2 files?

anubhava · Accepted Answer · 2021-09-24 14:33:32Z

Your approach of using grep -x won't work because it is looking for an exact match whereas file1 has 2 columns but file2 has only one. By removing -x it will give output but will output full lines not just the IPs e.g.:

grep -vwFf file2 file1 name2 12.90.543.87 name3 34.47.26.230

To get just the IPs you will have to use:

grep -vwFf file2 file1 | cut -d ' ' -f2

-w is very important here otherwise grep won't detect mismatch between 12.12.365.237 and 12.12.365.23.

You may use this better solution using awk:

awk 'FNR == NR {ips[$1]; next} !($2 in ips) {print $2}' file2 file1 12.90.543.87 34.47.26.230

markp-fuso · Accepted Answer · 2021-09-24 14:48:32Z

OP probably wants to enforce an exact word match instead of an exact line match, so replace the -x with a -w (same thing anubhava has mentioned):

$ grep -Fwvf File2.txt File1.txt name2 12.90.543.87 name3 34.47.26.230

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