Manipulators are special helper functions that help controlling input and output streams using operator >> or operator <<.

They all can be included by #include <iomanip>.

Remarks

Manipulators can be used in many ways. For example:

1. os.width(n); equals to os << std::setw(n); is.width(n); equals to is >> std::setw(n);

2. os.precision(n); equals to os << std::setprecision(n); is.precision(n); equals to is >> std::setprecision(n);

3. os.setfill(c); equals to os << std::setfill(c);

4. str >> std::setbase(base); or str << std::setbase(base); equals to

   str.setf(base ==  8 ? std::ios_base::oct :
               base == 10 ? std::ios_base::dec :
                   base == 16 ? std::ios_base::hex :
                        std::ios_base::fmtflags(0),
            std::ios_base::basefield);
   

5. os.setf(std::ios_base::flag); equals to os << std::flag; is.setf(std::ios_base::flag); equals to is >> std::flag; os.unsetf(std::ios_base::flag); equals to os << std::no ## flag; is.unsetf(std::ios_base::flag); equals to is >> std::no ## flag; (where ## - is concatenation operator) for next flags: boolalpha, showbase, showpoint, showpos, skipws, uppercase.

6. std::ios_base::basefield. For flags: dec, hex and oct:

   • os.setf(std::ios_base::flag, std::ios_base::basefield); equals to os << std::flag; is.setf(std::ios_base::flag, std::ios_base::basefield); equals to is >> std::flag; ( 1 )
   • str.unsetf(std::ios_base::flag, std::ios_base::basefield); equals to str.setf(std::ios_base::fmtflags(0), std::ios_base::basefield); ( 2 )

7. std::ios_base::adjustfield. For flags: left, right and internal:

   • os.setf(std::ios_base::flag, std::ios_base::adjustfield); equals to os << std::flag; is.setf(std::ios_base::flag, std::ios_base::adjustfield); equals to is >> std::flag; ( 1 )
   • str.unsetf(std::ios_base::flag, std::ios_base::adjustfield); equals to str.setf(std::ios_base::fmtflags(0), std::ios_base::adjustfield); ( 2 )

   ( 1 ) If flag of corresponding field previously set have already unset by unsetf. ( 2 ) If flag is set.

8. std::ios_base::floatfield.

   • os.setf(std::ios_base::flag, std::ios_base::floatfield); equals to os << std::flag; is.setf(std::ios_base::flag, std::ios_base::floatfield); equals to is >> std::flag;

   for flags: fixed and scientific.

   • os.setf(std::ios_base::fmtflags(0), std::ios_base::floatfield); equals to os << std::defaultfloat; is.setf(std::ios_base::fmtflags(0), std::ios_base::floatfield); equals to is >> std::defaultfloat;

9. str.setf(std::ios_base::fmtflags(0), std::ios_base::flag); equals to str.unsetf(std::ios_base::flag) for flags: basefield, adjustfield, floatfield.

10. os.setf(mask) equals to os << setiosflags(mask); is.setf(mask) equals to is >> setiosflags(mask); os.unsetf(mask) equals to os << resetiosflags(mask); is.unsetf(mask) equals to is >> resetiosflags(mask);

For almost all mask of std::ios_base::fmtflags type.

Stream manipulators

Output stream manipulators

Input stream manipulators