extern ostream cerr;

Standard output stream for errors

cerr is an object of class ostream that represents the standard error stream. It is associated with the cstdio stream stderr.

By default, most systems have their standard error output set to the console, where text messages are shown, although this can generally be redirected.

Because cerr is an object of class ostream, we can write characters to it either as formatted data using for example the insertion operator (ostream::operator<<) or as unformatted data using the write member function, among others (see ostream).

See also