Collecting data into one text file maintaining the original directory name, for loop, bash

I have a random folders names structure directories as below:

Main_directory 
    |__folder1
    |  |__file.txt
    |
    |__Case4
    |  |__file.txt
    |
    |__setup0
    |  |__file.txt
    |
    |__Case3
    |  |__file.txt

Each file.txt has one value e.g. -300. I am trying to loop through those folders with the random naming and collect the data in one text file in the Main directory maintaining the original directory name as below:

Main_directory 
    |__folder1
    |  |__file.txt  e.g. value of -300
    |
    |__Case4
    |  |__file.txt  e.g. value of 1000
    |
    |__setup0
    |  |__file.txt  e.g. value of -0.0005
    |
    |__Case3
    |  |__file.txt e.g. value of -349.666
    |
   results.txt

The result.txt should contain as below:

folder1 -300
Case4   1000
setup0 -0.0005
Case3  -349.666

Answer

In oneliner form:

for f in $(find . -mindepth 1 -maxdepth 1 -type d -printf "%Pn"); do printf $f >> result.txt; printf " " >> result.txt; cat $f/file.txt >> result.txt; done

In readable many liner form:

for f in $(find . -mindepth 1 -maxdepth 1 -type d -printf "%Pn"); do 
    printf $f >> result.txt; 
    printf " " >> result.txt; 
    cat $f/file.txt >> result.txt;
done

How it works:

1. Find all sub-directories, that are exactly sub-directories(not sub sub-directories), and print them without the leading ./:

find . -mindepth 1 -maxdepth 1 -type d -printf "%Pn"

2. Append the filename to result.txt, without adding a newline:

printf $f >> result.txt;

3. Add a space:

printf " " >> result.txt;

4. Add the file.txt contents:

cat $f/file.txt >> result.txt;

One disadvantage of this approach is that it requires file.txt to have a trailing newline. You can fairly easily fix this with a printf "n" >> result.txt.