Constructing Output Stream Objects

2021-08-03

If you use only the predefined cout, cerr, or clog objects, you do not need to construct an output stream. You must use constructors for:

Output File Stream Constructors
Output String Stream Constructors

Output File Stream Constructors

You can construct an output file stream in one of two ways:

Use the default constructor, and then call the open member function.

ofstream myFile; // Static or on the stack
myFile.open("filename");

ofstream* pmyFile = new ofstream; // On the heap
pmyFile->open("filename");

Specify a filename and mode flags in the constructor call.
```
ofstream myFile("filename", ios_base::out);
```

Output String Stream Constructors

To construct an output string stream, you can use ostringstream in the following way:

using namespace std;
// ...
ostringstream myString;
myString << "this is a test" << ends;

string sp = myString.str(); // Obtain string
cout << sp << endl;

The ends "manipulator" adds the necessary terminating null character to the string.

See also