`<ios>`

Article
12/07/2021

Defines several types and functions basic to the operation of iostreams. This header is typically included for you by another iostream headers; you rarely include it directly.

Requirements

Header: <ios>

Namespace: std

Note

The <ios> library uses the #include <iosfwd> statement.

Remarks

A large group of functions are manipulators. A manipulator declared in <ios> alters the values stored in its argument object of class ios_base. Other manipulators perform actions on streams controlled by objects of a type derived from this class, such as a specialization of one of the class templates basic_istream or basic_ostream. For example, noskipws(str) clears the format flag ios_base::skipws in the object str, which can be of one of these types.

You can also call a manipulator by inserting it into an output stream or extracting it from an input stream, because of special insertion and extraction operations supplied for the classes derived from ios_base. For example:

istr>> noskipws;

calls noskipws(istr).

Members

Typedefs

Name	Description
ios	Supports the ios class from the old iostream library.
streamoff	Supports internal operations.
streampos	Holds the current position of the buffer pointer or file pointer.
streamsize	Specifies the size of the stream.
wios	Supports the wios class from the old iostream library.
wstreampos	Holds the current position of the buffer pointer or file pointer.

Manipulators

Name	Description
boolalpha	Specifies that variables of type bool appear as `true` or `false` in the stream.
dec	Specifies that integer variables appear in base 10 notation.
defaultfloat	Configures the flags of an `ios_base` object to use a default display format for float values.
fixed	Specifies that a floating-point number is displayed in fixed-decimal notation.
hex	Specifies that integer variables appear in base 16 notation.
hexfloat
internal	Causes a number's sign to be left justified and the number to be right justified.
left	Causes text that is not as wide as the output width to appear in the stream flush with the left margin.
noboolalpha	Specifies that variables of type bool appear as 1 or 0 in the stream.
noshowbase	Turns off indicating the notational base in which a number is displayed.
noshowpoint	Displays only the whole-number part of floating-point numbers whose fractional part is zero.
noshowpos	Causes positive numbers to not be explicitly signed.
noskipws	Cause spaces to be read by the input stream.
nounitbuf	Causes output to be buffered and processed when the buffer is full.
nouppercase	Specifies that hexadecimal digits and the exponent in scientific notation appear in lowercase.
oct	Specifies that integer variables appear in base 8 notation.
right	Causes text that is not as wide as the output width to appear in the stream flush with the right margin.
scientific	Causes floating point numbers to be displayed using scientific notation.
showbase	Indicates the notational base in which a number is displayed.
showpoint	Displays the whole-number part of a floating-point number and digits to the right of the decimal point even when the fractional part is zero.
showpos	Causes positive numbers to be explicitly signed.
skipws	Cause spaces to not be read by the input stream.
unitbuf	Causes output to be processed when the buffer is not empty.
uppercase	Specifies that hexadecimal digits and the exponent in scientific notation appear in uppercase.

Error Reporting

Name	Description
io_errc
is_error_code_enum
iostream_category
make_error_code
make_error_condition

Classes

Name	Description
basic_ios	The class template describes the storage and member functions common to both input streams (of class template basic_istream) and output streams (of class template basic_ostream) that depend on the template parameters.
fpos	The class template describes an object that can store all the information needed to restore an arbitrary file-position indicator within any stream.
ios_base	The class describes the storage and member functions common to both input and output streams that do not depend on the template parameters.