Redirecting input using stdin - c++

Question

I am writing a short program to sort an array of integers. I am having trouble opening my input file which is "prog1.d". The assignment has asked to create a symbolic link in the programs directory, and I after creating the object & executable, we invoke the program as follows...
prog1.exe < prog1.d &> prog1.out
I know my bubble sort works correctly & efficiently because I have used my own test 'txt' file.
The assignment says:
Your program gets the random integers from stdin and puts them in an array, sorts the integers in the array in ascending order, and then displays the contents of the array on stdout.
How do I read the file using 'cin' until EOF & add the integers to my array a[] ?
Here is my code so far:
int main( int argc, char * argv[] )
{
int a[SIZE];
for ( int i=1; i<argc; i++)
{
ifstream inFile; // declare stream
inFile.open( argv[i] ); // open file
// if file fails to open...
if( inFile.fail() )
{
cout << "The file has failed to open";
exit(-1);
}
// read int's & place into array a[]
for(int i=0; !inFile.eof(); i++)
{
inFile >> a[i];
}
inFile.close(); // close file
}
bubbleSort(a); // call sort routine
printArr(a); // call print routine
return 0;
}
I know that opening a stream is the wrong way to do this, I just was using it for a test 'txt' file I was using to make sure my sorting worked. The teacher said we should redirect the input to 'cin' like someone was entering integers on a keyboard.
Any help would be greatly appreciated.

Answer 1

When you're using redirection on the command line, argv does not contain the redirection. Instead, the specified file simply becomes your stdin/cin. So you don't need to (and shouldn't try to) open it explicitly -- just read from the standard input, as you would read from the terminal when input isn't redirected.

Answer 2

Since you are piping the file on the stdin, you don't have the file name on argv[1], just read the stdin as the user was typing at the console, for example using cin:
cin.getline (...);

Answer 3

The other answers are completely correct, but here's the rewritten code to claify:
int main( int argc, char * argv[] )
{
int a[SIZE];
int count = 0;
// read int's & place into array a[]
//ALWAYS check the boundries of arrays
for(int i=0; i<SIZE; i++)
{
std::cin >> a[i];
if (std::cin)
count = count + 1;
else
break;
}
bubbleSort(a, count); // call sort routine
printArr(a, count); // call print routine
return 0;
}

Answer 4

As everyone has stated, use std::cin directly -- you don't need to open the input file, your shell has already done that for you.
But, please, please, please, don't use cin.eof() to test to see if you have reached the end of your input. If your input is flawed, your program will hang. Even if your input isn't flawed, your program may (but won't necessarily) run the loop one extra time.
Try this loop instead:
int a[SIZE];
int i = 0;
while( std::cin >> a[i]) {
++i;
}
Or, add robustness by using std::vector which will automatically grow:
std::vector<int> a;
int i;
while(std::cin >> i) {
a.push_back(i);
}
Or, use generic algorithms:
#include <iterator>
#include <algorithm>
...
std::vector<int> a;
std::copy(std::istream_iterator<int>(std::cin),
std::istream_iterator<int>(),
std::back_inserter(a));