Bash find fails to return all matching files when called from a script - linux

Question

Running the same command from the command line and from a bash script produces different results on Ubuntu 16.04.
I have a folder with the following contents:
├── audio
│   └── delete_me.mp3
├── words
│   └── audio
│   └── delete_me.mp3
│   └── images
│   └── delete_me.jpg
└── keep_me.txt
I have a bash script named findKeepers.sh:
#!/usr/bin/env bash
findKeepers () {
local dir=$1
echo "$(find $dir -type f ! -name delete_me*)"
}
findKeepers /path/to/directory
I expect it to output the path to the keep_me.txt file. Instead, I get a blank line.
 
If I run what seems to me to be identical commands from the command line, I get what I expect:
dir=/path/to/directory; echo "$(find $dir -type f ! -name delete_me*)"
/path/to/directory/keep_me.txt
If search instead for all files not called keep_me, the bash script ignores the audio folder. Here's another bash script called findUnwanted.sh:
#!/usr/bin/env bash
findUnwanted () {
local dir=$1
echo "$(find $dir -type f ! -name keep_me*)"
}
findUnwanted /path/to/directory
Here's the result:
$ ./findUnwanted.sh
/path/to/directory/words/audio/delete_me.mp3
/path/to/directory/words/images/delete_me.jpg
If I run the same thing from the command line, I get all three delete_me files:
$ dir=/path/to/directory; echo "$(find $dir -type f ! -name keep_me*)"
/path/to/directory/words/audio/delete_me.mp3
/path/to/directory/words/images/delete_me.jpg
/path/to/directory/audio/delete_me.mp3
It seems to me that the bash script starts by going deep into the words folder, and then does not come out again to search adjacent folders or files. Is there something special about the #!/usr/bin/env bash environment that makes it do this? Or is there some other difference that I'm not seeing?
CODA: I'm guessing it was pilot error, because after more modifications it started working for me again. For anyone who is interested, the final version of my function is shown below.
#!/usr/bin/env bash
# Returns 1 if the given directory contains only placeholder files, or
# 0 if the directory contains something worth keeping
checkForDeletion () {
local _dir=$1
local _temp=$(find "$_dir" -type f ! -regex '.*\(unused.txt\|delete_me.*\)')
if [ -z "$_temp" ]
then
return 1
fi
}
I use it like this:
parent=/path/to/parent/
for dir in $parent*/
do
checkForDeletion $dir
if [ $? = 1 ]
then
echo "DELETE? $dir" # rm -rf $dir
fi
done

Answer 1

I am guessing that your '!' is breaking the whole pipe. Try using '-not' instead, so your first code snippet would look like this:
echo "$(find $dir -type f -not -name delete_me*)"
I am not that good at explaining where you should escape special characters and where not, but the fact that things work differently when using that outside function suggests that escaping may be the issue.