Regex with positive and negative selection in for loop to iterate through a list of files

I embarrassingly struggle to iterate through multiple files selected one the basis of multiple criteria (defined by a regex). For example from the files listed below I'd like to select only files with txt extension, except the ones containing a string "cat":

mousecatdog.txt
dogcowfox.gif
dogmousecat.txt
dogmousepig.txt

So I'd like to get only dogmousepig.txt from this list.

I tried to use negative lookaheads, but I am getting an error:

syntax error near unexpected token `('

Of course looked at other threads on the forum, and tried to fix the problem by adding parentheses () or enabling shopt -s extglob, but to no avail.

I'm using mac and the script is in bash.

 #!/bin/bash
    for FILE in ^((?!cat).)*.txt
     do
      printf "\$FILE\n" 
     done

Solution

Bash uses wildcard expansion, not regular expressions in your example.

I see two fairly easy solutions:

1- use a wildcard for the positive selection and an RE for the negative selection, just like @Wiktor Stribizew said in his comment:

for FILE in *.txt; do
   if [[ ! $FILE =~ cat ]]; then
      printf "$FILE\n" 
   fi
done

2- grep out the output of the wildcard expansion (although this won't work correctly if there are spaces in your file names):

for FILE in `\ls -1 *.txt | grep -v cat`; do
   printf "$FILE\n"
done