It is common for people to name directories as dir1, dir2, and so on. When there are ten or more directories, the operating system displays them in dictionary order, as dir1, dir10, dir11, dir12, dir2, dir3, and so on.
That is irritating, and it is easy to fix. Provide a comparator that compares strings that end in digit sequences in a way that makes sense to a human. First compare the part before the digit as strings, and then compare the numeric values of the digits.
Your program should read in a text file with the list of directories to sort and should output them to the screen. If an error is found while reading the text file, the user should be allowed to choose another file. There will be one directory name per line of the file.