Unsetf

Unsetf is a member function of the C++ standard library’s I/O stream base class (std::ios_base) and all derived stream types. It clears the format flags currently set on a stream by unsetting the bits specified by its argument. The operation affects only the stream’s format state and does not modify other aspects of the stream.

Format flags are defined in std::ios_base::fmtflags and include both individual flags (such as boolalpha, showbase, showpoint, uppercase, skipws, etc.) and groups known as basefield, adjustfield, and floatfield. Unsetf takes a mask of type fmtflags and clears the corresponding bits in the stream’s format state. If a group flag is supplied, the bits within that group are cleared accordingly. Passing a zero mask has no effect.

Usage examples illustrate common patterns. For instance, to revert floating-point formatting after using fixed or scientific, you can write: std::cout.unsetf(std::ios::floatfield); This clears the floatfield bits and restores default floating-point formatting. To remove any base-related formatting, you might call: std::cout.unsetf(std::ios::basefield); Clearing show-related or other individual flags can be done by unsetting the specific flag, such as std::cout.unsetf(std::ios::showpos).

Unsetf is often used together with setf to switch between formats and then return to defaults. It is declared in <ios> and is available on all standard streams, including std::cin, std::cout, and std::cerr. See also setf, std::ios_base::fmtflags, and the ios_base class.