how to subtract the two files in linux - linux

Question

I have two files like below:
file1
"Connect" CONNECT_ID="12"
"Connect" CONNECT_ID="11"
"Connect" CONNECT_ID="122"
"Connect" CONNECT_ID="109"
file2
"Quit" CONNECT_ID="12"
"Quit" CONNECT_ID="11"
The file contents are not exactly same but similar to above and the number of records are minimum 100,000.
Now i want to get the result as show below into file1 (means the final result should be there in file1)
"Connect" CONNECT_ID="122"
"Connect" CONNECT_ID="109"
I have used a while loop something like below:
awk {'print $2'} file2 | sed "s/CONNECTION_ID=//g" > sample.txt
while read actual; do
grep -w -v $actual file1 > file1_tmp
mv -f file1_tmp file1
done < sample.txt
Here I have adjusted my code according to example. So it may or may not work.
My problem is the loop is repeating for more than 1 hour to complete the process.
So can any one suggest me how to achieve the same with any other ways like using diff or comm or sed or awk or any other linux command which will run faster?
Here mainly I want to eliminate this big typical while loop.

Answer 1

Most UNIX tools are line based and as you don't have whole line matches that means grep, comm and diff are out the window. To extract field based information like you want awk is perfect:
$ awk 'NR==FNR{a[$2];next}!($2 in a)' file2 file1
"Connect" CONNECT_ID="122"
"Connect" CONNECT_ID="109"
To store the results back to file1 you'll need to redict the output to a temporary file and then move the file into file1 like so:
$ awk 'NR==FNR{a[$2];next}!($2 in a)' file2 file1 > tmp && mv tmp file1
Explanation:
The awk variable NR increments for every record read, that is each line in every file. The FNR variable increments for every record but gets reset for every file.
NR==FNR # This condition is only true when reading file1
a[$2] # Add the second field in file1 into array as a lookup table
next # Get the next line in file1 (skips any following blocks)
!($2 in a) # We are now looking at file2 if the second field not in the look up
# array execute the default block i.e print the line
To modify this command you just need to change the fields that matched. In your real case if you want to match field 1 from file1 with field 4 from file2 then you would do:
$ awk 'NR==FNR{a[$1];next}!($4 in a)' file2 file1

Answer 2

This might work for you (GNU sed):
sed -r 's|\S+\s+(\S+)|/\1/d|' file2 | sed -f - -i file1

Answer 3

The tool best suited to this job is join(1). It joins two files based on values in a given column of each file. Normally it just outputs the lines that match across the two files, but it also has a mode to output the lines from one of the files that do not match the other file.
join requires that the files be sorted on the field(s) you are joining on, so either pre-sort the files, or use process substitution (a bash feature - as in the example below) to do it on the one command line:
$ join -j 2 -v 1 -o "1.1 1.2" <(sort -k2,2 file1) <(sort -k2,2 file2)
"Connect" CONNECT_ID="122"
"Connect" CONNECT_ID="109"
-j 2 says to join the files on the second field for both files.
-v 1 says to only output fields from file 1 that do not match any in file 2
-o "1.1 1.2" says to order the output with the first field of file 1 (1.1) followed by the second field of file 1 (1.2). Without this, join will output the join column first followed by the remaining columns.

Answer 4

You may need to analyze file2 at fist, and append all ID which have appered to a cache(eg. memory)
Than scan file1 line by line to adjust whether the ID in the cache.
python code like this:
#!/usr/bin/python
# -*- coding: utf-8 -*-
import re
p = re.compile(r'CONNECT_ID="(.*)"')
quit_ids = set([])
for line in open('file2'):
m = p.search(line)
if m:
quit_ids.add(m.group(1))
output = open('output_file', 'w')
for line in open('file1'):
m = p.search(line)
if m and m.group(1) not in quit_ids:
output.write(line)
output.close()

Answer 5

The main bottleneck is not really the while loop, but the fact that you rewrite the output file thousands of times.
In your particular case, you might be able to get away with just this:
cut -f2 file2 | grep -Fwvf - file1 >tmp
mv tmp file1
(I don't think the -w option to grep is useful here, but since you had it in your example, I retained it.)
This presupposes that file2 is tab-delimited; if not, the awk '{ print $2 }' file2 you had there is fine.