Fastest way of finding differences between two files in unix

Question

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

User · Accepted Answer

You could try        comm -13  lt  sort file1   lt  sort file2   gt  file3   or  grep -Fxvf file1 file2  gt  file3   or  diff file1 file2   grep   lt     sed  s   lt   g    gt  file3   or  join -v 2  lt  sort file1   lt  sort file2   gt  file3

User · Answer

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

User · Answer

Another option   sort file1 file2   uniq -u  gt  file3   If you want to see just the duplicate entries use  uniq -d  option   sort file1 file2   uniq -d  gt  file3

User · Answer

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

[linux] Fastest way of finding differences between two files in unix?

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