Question

I want to use the push_back function to fill my vector with lines from a text file. But it overwrites all entries with the last line. Here is the source code:

  int main() {
    std::vector<char*> lines;
    FILE* file;
    file = fopen("textfile.txt", "r");
    const size_t max_line_length = 1000;
    char line[max_line_length + 1];
    while ( !feof(file)) {
      fgets(line, max_line_length, file);
      lines.push_back(line);
    }
    fclose(file);
 }

Hope somebody can help.

Answer 1

You are overwriting Line, and that’s actually the only thing your are storing, since you never make deep copies. Try this instead:

int main() {
    std::vector<std::string> lines; // <- change this!
    FILE* file;
    file = fopen("textfile.txt", "r");
    const size_t max_line_length = 1000;
    char line[max_line_length + 1];
    while ( !feof(file)) {
      fgets(line, max_line_length, file);
      lines.push_back(line);
    }
    fclose(file);
 }