Open files from documents in loop

I want to open several files in a for loop.

Anyone who can help me with this?

For now I tried this:

    a = "/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-"
    b = r
    c = ".csv"
    filename = strcat(a,b,c);
    filename = convertCharsToStrings(filename);
    truck1 = readtable(filename, opts);

How can I make r the variable (1 to 20)?

[Chunru]

a = "/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-";
c = ".csv";
for r=1:20
    filename = sprintf('%s%d%s', a, r, c);
    disp(filename)
    %truck1 = readtable(filename, opts);
end

/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-1.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-2.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-3.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-4.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-5.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-6.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-7.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-8.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-9.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-10.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-11.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-12.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-13.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-14.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-15.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-16.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-17.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-18.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-19.csv
/Users/diontheunissen/Documents/Smart_Driver/RawData/Scania/e-20.csv