Patterns and filename-safe iteration

The idea

Bash patterns such as *.txt are not regular expressions. Inside [[ $name == *.txt ]], the unquoted right side is a pattern, while quoting that right side makes it literal text. The left side remains a value under the special conditional syntax, avoiding ordinary word splitting. Decide whether a caller supplies a pattern or ordinary text before choosing the comparison form.

Filename expansion has a separate empty-match policy. By default, an unmatched glob can remain as a literal word; nullglob removes an unmatched pattern from the result. A robust file loop must choose that policy and quote each expanded filename when passing it onward. Spaces and wildcard characters inside actual filenames are data, so never reconstruct a command by joining names into one string for later evaluation.

name="report one.txt"
if [[ $name == *.txt ]]; then printf 'text file\n'; fi
if [[ $name == "*.txt" ]]; then printf 'literal match\n'; fi

text file

The first comparison interprets the suffix pattern; the second asks whether the whole name literally equals *.txt.