std::ios_base(3)

NAME
std::ios_base - std::ios_base

Synopsis
   Defined in header <ios>
   class ios_base;
   The class ios_base is a multipurpose class that serves as the base class for all I/O
   stream classes. It maintains several kinds of data:
   1) state information: stream status flags.
   2) control information: flags that control formatting of both input and output
   sequences and the imbued locale.
   3) private storage: indexed extensible data structure that allows both long and
   void* members, which may be implemented as two arbitrary-length arrays or a single
   array of two-element structs or another container.
   4) callbacks: arbitrary number of user-defined functions to be called from imbue(),
   std::basic_ios::copyfmt(), and ~ios_base().
   Typical implementation holds member constants corresponding to all values of
   fmtflags, iostate, openmode, and seekdir shown below, member variables to maintain
   current precision, width, and formatting flags, the exception mask, the buffer error
   state, a resizeable container holding the callbacks, the currently imbued locale,
   the private storage, and a static integer variable for xalloc().

Member functions
   constructor constructs the object
                     (protected member function)
   destructor destructs the object
   [virtual] (virtual public member function)
   operator= assigns to the stream
                     (public member function)

Formatting
   flags manages format flags
                     (public member function)
   setf sets specific format flag
                     (public member function)
   unsetf clears specific format flag
                     (public member function)
   precision manages decimal precision of floating point operations
                     (public member function)
   width manages field width
                     (public member function)

Locales
   imbue sets locale
                     (public member function)
   getloc returns current locale
                     (public member function)

Internal extensible array
   xalloc returns a program-wide unique integer that is safe to use as index
   [static] to pword() and iword()
                     (public static member function)
                     resizes the private storage if necessary and access to the long
   iword element at the given index
                     (public member function)
                     resizes the private storage if necessary and access to the void*
   pword element at the given index
                     (public member function)

Miscellaneous
   register_callback registers event callback function
                     (public member function)
   sync_with_stdio sets whether C++ and C I/O libraries are interoperable
   [static] (public static member function)

Member classes
   failure stream exception
                     (public member class)
   Init initializes standard stream objects
                     (public member class)

Member types and constants
   Type Explanation
                  stream open mode type
                  The following constants are also defined:
                  Constant Explanation
                  app seek to the end of stream before each write
                  binary open in binary mode
   openmode in open for reading
                  out open for writing
                  trunc discard the contents of the stream when
                        opening
                  ate seek to the end of stream immediately after
                        open
                  noreplace (C++23) open in exclusive mode
                  (typedef)
                  formatting flags type
                  The following constants are also defined:
                  Constant Explanation
                  dec use decimal base for integer I/O: see std::dec
                  oct use octal base for integer I/O: see std::oct
                  hex use hexadecimal base for integer I/O: see std::hex
                  basefield dec | oct | hex. Useful for masking operations
                  left left adjustment (adds fill characters to the right): see
                        std::left
                  right right adjustment (adds fill characters to the left): see
                        std::right
                  internal internal adjustment (adds fill characters to the internal
                        designated point): see std::internal
                  adjustfield left | right | internal. Useful for masking
                        operations
                        generate floating point types using scientific notation,
                  scientific or hex notation if combined with fixed: see
                        std::scientific
   fmtflags generate floating point types using fixed notation, or
                  fixed hex notation if combined with scientific: see
                        std::fixed
                  floatfield scientific | fixed. Useful for masking operations
                  boolalpha insert and extract bool type in alphanumeric format: see
                        std::boolalpha
                        generate a prefix indicating the numeric base for integer
                  showbase output, require the currency indicator in monetary I/O:
                        see std::showbase
                  showpoint generate a decimal-point character unconditionally for
                        floating-point number output: see std::showpoint
                  showpos generate a + character for non-negative numeric output:
                        see std::showpos
                  skipws skip leading whitespace before certain input operations:
                        see std::skipws
                  unitbuf flush the output after each output operation: see
                        std::unitbuf
                        replace certain lowercase letters with their uppercase
                  uppercase equivalents in certain output operations: see
                        std::uppercase
                  (typedef)
                  state of the stream type
                  The following constants are also defined:
                  Constant Explanation
   iostate goodbit no error
                  badbit irrecoverable stream error
                  failbit input/output operation failed (formatting or extraction
                        error)
                  eofbit associated input sequence has reached end-of-file
                  (typedef)
                  seeking direction type
                  The following constants are also defined:
   seekdir Constant Explanation
                  beg the beginning of a stream
                  end the ending of a stream
                  cur the current position of stream position indicator
                  (typedef)
   event specifies event type
                  (enum)
   event_callback callback function type
                  (typedef)

Deprecated member types
   Type Explanation
   io_state (deprecated) integer type that may be used like iostate
   open_mode (deprecated) integer type that may be used like openmode
   seek_dir (deprecated) integer type that may be used like seekdir (until C++17)
   streamoff (deprecated) unspecified type that may be used like
                        off_type, not necessarily std::streamoff
   streampos (deprecated) unspecified type that may be used like
                        pos_type, not necessarily std::streampos
   Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
      DR Applied to Behavior as published Correct behavior
                       std::ios_base defined operator~, operator&
   LWG 1357 C++98 and operator| for types openmode, fmtflags and removed these
   (N3110) iostate, violating the requirements of definitions
                       BitmaskType^[1]
    1. ↑ A BitmaskType needs to support bitwise opertaions on its own. The bitwise
       operation support should not be provided externally.

See also
   basic_ios manages an arbitrary stream buffer
             (class template)