Bash scope issue (?) when incrementing variable

Question

I have code like this:

#!/bin/bash

n=0
for file in *.txt
do
        tail -c1 $file | read -r _ || (
                ((n++))
                echo "$file is missing a final newline, issue #$n"
        )
done

But when I run it, the numbers aren't incrementing:

a.txt is missing a final newline, issue #1

b.txt is missing a final newline, issue #1

How can I fix this? It looks like a scope issue, since the 0 is incremented to 1 as though the previous increment was ignored.

Answer 1

your commands embedded between parentheses runs as a subshell, each subshell in the loop starts over with the value of n set at the parent level (n=0).

Just change the parenthesis to curly braces (a terminal semicolon or newline is required).