tar processing files multiple times with find -newer

Question

I'm trying to use tar(1) to create an archive of files newer than a specific file (fileA). However, when I use find(1) to obtain the list of files to pass to tar, some files are listed multiple times:

$ touch fileA
$ mkdir test
$ touch test/{fileB,fileC}
$ tar -c -v $(find test -newer fileA) > test.tar
test/
test/fileC
test/fileB
test/fileC
test/fileB

Using xargs(1) to pass the list of files to tar results in similar behavior:

$ find test -newer fileA | xargs tar -c -v > test.tar
test/
test/fileC
test/fileB
test/fileC
test/fileB

Using sort(1) and uniq(1) to remove duplicates doesn't work either:

$ find test -newer fileA | sort | uniq | xargs tar -c -v > test.tar
test/
test/fileC
test/fileB
test/fileB
test/fileC

Is there a way for tar to only include each file newer than fileA once?

Edit: I'm specifically looking for a solution that doesn't involve GNU extensions to tar (for example, which would work with suckless tar).

Answer 1

find test -newer fileA

finds the test directory as well as the individual files therein, so tar adds test (and all its contents), then test/fileB and test/fileC.

Tighten your find to avoid this:

tar -c -v $(find test -type f -newer fileA) > test.tar

Note that using command substitution in this way can cause issues e.g. with filenames containing spaces or wildcards; to avoid that, use

find test -type f -newer fileA -print0 | tar -c -v --null -T- -f - > test.tar

(with GNU find and tar), or

find test -type f -newer fileA -exec tar cvf - {} + > test.tar

(assuming you don’t have too many files to archive).

Answer 2

You can try something like:

tar --newer=fileA cvf test.tar test