c++ nested while loop runs only once - c++

Question

Please can you advise, why the inner loop runs only once?
I'd like to add suffix to each line of input file and then store the result in output file.
thanks
For example:
Input file contains:
AA
AB
AC
Suffix file contains:
_1
_2
Output file should contain:
AA_1
AB_1
AC_1
AA_2
AB_2
AC_2
My result is :
AA_1
AB_1
AC_1
Code:
int main()
{
string line_in{};
string line_suf{};
string line_out{};
ifstream inFile{};
ofstream outFile{"outfile.txt"};
ifstream suffix{};
inFile.open("combined_test.txt");
suffix.open("suffixes.txt");
if (!inFile.is_open() && !suffix.is_open()) {
perror("Error open");
exit(EXIT_FAILURE);
}
while (getline(suffix, line_suf)) {
while (getline(inFile, line_in))
{
line_out = line_in + line_suf;
outFile << line_out << endl;
}
inFile.close();
outFile.close();
}
}

Answer 1

IMHO, a better method is to read the files into vectors, then iterate through the vectors:
std::ifstream word_base_file("combined_test.txt");
std::ifstream suffix_file("suffixes.txt");
//...
std::vector<string> words;
std::vector<string> suffixes;
std::string text;
while (std::getline(word_base_file, text))
{
words.push_back(text);
}
while (std::getline(suffix_file, text))
{
suffixes.push_back(text);
}
//...
const unsigned int quantity_words(words.size());
const unsigned int quantity_suffixes(suffixes.size());
for (unsigned int i = 0u; i < quantity_words; ++i)
{
for (unsigned int j = 0; j < quantity_suffixes; ++j)
{
std::cout << words[i] << suffix[j] << "\n";
}
}
Edit 1: no vectors
If you haven't learned about vectors or like to thrash your storage device you could try this:
std::string word_base;
while (std::getline(inFile, word_base))
{
std::string suffix_text;
while (std::getline(suffixes, suffix_text))
{
std::cout << word_base << suffix_text << "\n";
}
suffixes.clear(); // Clear the EOF condition
suffixes.seekg(0); // Seek to the start of the file (rewind).
}
Remember, after the inner while loop, the suffixes file is at the end; no more reads can occur. Thus the file needs to be positioned at the start before reading. Also, the EOF state needs to be cleared before reading.