Compare two files and remove all the contents of one file from another

Shell Programming and Scripting
1

Hi,

I have two files, in which the second file has exactly the same contents of the first file with some additional records. Now, if I want to remove those matching lines from file2 and print only the extra contents which the first file does not have, I could use the below unsophisticated command, consider f1 and f2 are the two files

var=`cat f1`
grep -v "$var" f2

but I need a more optimal solution with fast and reliable with less memory consumption.

I have found these 2 lines of code, but it does not work for files having lengthier lines:

fgrep -v -x -f f2 f1  
awk 'NR==FNR {b[$0]; next} !($0 in b)' f2 f1
2 
> cat file70
abc
def
ghi
jkl
mno
pqr
stu
vwx
yz
123
456
789
0

> cat file71
abc
def
ghi
jkl
mno
pqr
stu
vwx
yz
bash ksh
123
456
789
0
unix.com

> diff file70 file71 | grep "^>" | cut -c3-
bash ksh
unix.com
3

Hi,

to print the different lines of two files try:

comm -3 file1 file2

and for further informations

man comm

Kind regards

Chris

4

Thanks to you all for the suggestions. But anyone has any awk, perl code to do this task?

And Also, the below perl code will remove duplicate, non-consecutive lines based on the last field without sorting. Now, please tell me, what should I change in this code in order to print unique lines of a file by just not seeing the last field but the entire line (the whole record)?

perl -ane'print unless $_{$F[-1]}++'