I want to find the difference between two files and then put only the differences in a third file. I saw different approaches using awk, diff and comm. Are there any more ?
eg.Compare two files line by line and generate the difference in another file
eg.Copy differences between two files in unix
I need to know which is the fastest way of finding all the differences and listing them in a file for each of the cases below -
Case 1 - file2 = file1 + extra text appended.
Case 2 - file2 and file1 are different.
You could try..
comm -13 <(sort file1) <(sort file2) > file3
or
grep -Fxvf file1 file2 > file3
or
diff file1 file2 | grep "<" | sed 's/^<//g' > file3
or
join -v 2 <(sort file1) <(sort file2) > file3
Another option:
sort file1 file2 | uniq -u > file3
If you want to see just the duplicate entries use "uniq -d" option:
sort file1 file2 | uniq -d > file3
You could also try to include md5-hash-sums or similar do determine whether there are any differences at all. Then, only compare files which have different hashes...
This will work fast:
Case 1 - File2 = File1 + extra text appended.
grep -Fxvf File2.txt File1.txt >> File3.txt
File 1: 80 Lines File 2: 100 Lines File 3: 20 Lines
Source: Stackoverflow.com