重复地重定向std :: cin流

Question

i want to read the first part of my input from *.txt and get the rest manually from user. for instance:

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string a[100];
    for (int i=0;i<100;i++)
        cin >> a[i];
    for (int i=0;i<100;i++)
        cout << a[i] << endl;
}

if i run the above code like ./a.out < input.txt and input.txt only consists of 10 words for example, how can i redirect the input stream back to console so that i get the rest from user ?

Answer 1

You said:

i want to read the first part of my input from *.txt and get the rest manually from user.

If this is the only requirement, I would suggest a change of strategy.

1. Get the name of the input file from the command line.
2. Read as much data as you can from the file.
3. Then switch to reading the rest of the data from cin .

For example:

#include <iostream>
#include <string>
using namespace std;

int main(int argc, char** argv)
{
   string a[100];
   int count = 0;

   if ( argc > 1 )
   {
      ifstream infile(argv[1]);
      while (count < 100)
      {
         infile >> a[count];
         if ( infile )
         {
            ++count;
         }
         else
         {
            break;
         }
      }
   }

   for (int i=count;i<100;i++)
      cin >> a[i];
   for (int i=0;i<100;i++)
      cout << a[i] << endl;
}