A particular diff

Question

I have 2 files: list-folder1.txt and list-folder2.txt. These files are derived from the ls -1R command run on linux in their respective folders (similar folders consisting of thousands of files and some subdirectories). I would like a difference.txt file with the list of files present in list-folder2.txt but not present in list-folder1.txt also indicating the folder. (Example: ls -1R examples > list-folder-old.txt is:

examples:
c
lua

examples/c:
Makefile
env.c
helloworld.c

examples/lua:
fizzbuzz.lua

ls -1R examples > list-folder.txt is:

examples:
c
lua
file1.txt

examples/c:
Makefile
env.c
file2.txt
helloworld.c

examples/lua:
file3.txt
fizzbuzz.lua

difference.txt shuold be:

examples:
file1.txt

examples/c:
file2.txt

examples/lua:
file3.txt

Is there an easy way in Reboland to solve this problem? Is it better to use read with parse or read/lines?

Answer 1

Given your example file, you can try using exclude to subtract the second set of lines from the first one. E.g.:

write/lines %difference.txt exclude read/lines %list-folder2.txt read/lines %list-folder1.txt

That should work for both Red and Rebol. In case of Red, if you want to use it from a batch script, I recommend downloading the "CLI Red" version from the download page.

Is it better to use read with parse or read/lines?

If the need is just to split the file into lines that can be directly processed, go with read/lines. If anything more than that is needed, then go with read then parse.