#!/bin/bash
cat "./directory_1/"*.txt > "directory_1.txt"
cat "./directory_2/"*.txt > "directory_2.txt"

#!/bin/bash
cat "./directory_1/"*.txt > "directory_1.txt";cat "./directory_2/"*.txt > "directory_2.txt"

line 2: $'r': command not found
: No such file or directorydirectory2.txt

for dir in */; do
    cat "$dir"/*.txt >"${dir%/}.txt"
done