find test and bash test do not give the same result, why?

Question

In my previous question In find -exec, how to substitue current file by {}?, I have asked about test with find. I want to find all files I do not own. So there is proper find command:

find . -type f ! -user "$USER"

but so should be this one as well:

find . -type f -exec bash -c '
    for pathname do
        [[ ! -O "$pathname" ]] && printf "%s\n" "$pathname"
    done' bash {} +

yet both gives different results .

1) if I do [command one] | wc -c --> 4121

But: [command two] | wc -c --> 236768 (PS: I am searching files in my $HOME).

Both gives different numbers of how many files they found.

2) Both still give in result files, that are directories (yes, directories I do not own and thus - permission denied). They give directories despite having find . -type f type files (not dirs) in argument of option, why? (When I ls -ld one of those directory, none is link or anything else)

Answer 1

Hmm ..., in my homedir, both commands work the same. 8-/

Nevertheless, you should redirect the stderr to /dev/null and use wc -l to correctly count the output.

find . -type f ! -user "$USER" 2>/dev/null | wc -l

find . -type f -exec bash -c '
    for pathname do
        [[ ! -O "$pathname" ]] && printf "%s\n" "$pathname"
    done' 2>/dev/null bash {} + | wc -l

From here you could redirect the results to text files and compare the files to look for differences.

find . -type f ! -user "$USER" 2>/dev/null > /tmp/file_1.txt
find . -type f -exec bash -c '
    for pathname do
        [[ ! -O "$pathname" ]] && printf "%s\n" "$pathname"
    done' 2>/dev/null bash {} + >/tmp/file_2.txt
diff /tmp/file_{1,2}.txt

If there are differences, take some of the excess files of /tmp/file_2.txt and investigate further why the file is not considered ' True if file exists and is owned by the effective user id'.

Answer 2

To avoid having find enter directories that are not actually accessible to you, you can use ! -executable -prune:

find . ! -executable -prune -type f ! -user "$USER"

The negated -executable test will be true for directories that you don't have access to, and -prune will remove these from find's search tree, stopping the utility from trying to access them, and thus avoiding generating permission errors.

The -executable test (as well as the analogous -readable and -writable tests) are non-standard and require GNU find.

I can't (yet) say anything about the differences in result as you have said nothing about these. Since the output varies so drastically in size, it ought to be trivial to find and examine cases where one command found something that the other command did not find.