比较两个文件并应用差异

Question

on a Linux based system, I can easily compare two files, eg:

diff file1.txt file2.txt

...and see the difference between them.

What if I want to take all lines that are unique to file2.txt and apply them to file1.txt so that file1.txt will now contain everything it had + lines from file2.txt that it didn't have before? Is there an easy way to do it?

Answer 1

Using patch

1. You can use diff 's output to create a patch file .

    diff original_file file_with_new_lines > patch_file 

2. You can edit patch_file to keep only the additions, since you only want the new lines.

3. Then you can use the patch command to apply this patch file:

    patch original_file patch_file 

Answer 2

If you don't mind appending the sorted diff to your file, you can use comm :

cat file1.txt <(comm -13 <(sort f1.txt) <(sort f2.txt)) > file1.txt.patched

or

comm -13 <(sort f1.txt) <(sort f2.txt) | cat file1.txt - > file1.txt.patched

This will append the unique lines from file2.txt to file1.txt.