使用指针读取和写入文件

Question

I am new to pointers and I have a task to read a 2d array from a file. I have to use the function which takes in a parameter (char * path).As you can see i am manually typing in which text file i want to open in the code but i think i have to use pointers as it is the parameter in my 'read_from_file' function. I am taking user inputs at command line to see which file they want to read from using the code below. I'm unsure how to use char* argv[] as parameter that will be passed on to my read_from_file(char *path) so that i can read from the file the user stated. My code for reading from a file works completely fine but i just want some help with the pointers.

int main(int argc, char* argv[]){

---

int read_from_file(char *path){



ifstream infile("file.txt");
string line;

std::vector<std::vector<int> > num;

std::string line;
while (std::getline(infile, line))

{
    std::vector<int> values;
    std::istringstream iss(line);
int value;
while (iss >> value)
{
    values.push_back(value);
}

num.push_back(values);
}
}

Answer 1

If you don't want anything fancy:

// Note: argv[0] is the name of the program itself, 1..n are actual arguments
for (int i = 1; i < argc; ++i) {
  read_from_file(argv[i]);
}

Then you can use that in your function:

std::ifstream infile(path);

Typically in C++ you should specify arguments like this as const char* .