C++ iomanip Library - setfill Function


The C++ function std::setfill behaves as if member fill were called with c as argument on the stream on which it is inserted as a manipulator (it can be inserted on output streams).

It is used to sets c as the stream's fill character.


Following is the declaration for std::setfill function.

setfill (char_type c);


c − The new fill character for the stream. char_type is the type of characters used by the stream (i.e., its first class template parameter, charT).

Return Value

It returns unspecified. This function should only be used as a stream manipulator.


Basic guarantee − if an exception is thrown, the stream is in a valid state.

Data races

The stream object on which it inserted is modified. Concurrent access to the same stream object may introduce data races.


In below example explains about setfill function.

#include <iostream>
#include <iomanip>

int main () {
   std::cout << std::setfill ('x') << std::setw (10);
   std::cout << 77 << std::endl;
   return 0;

Let us compile and run the above program, this will produce the following result −