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std::ios_base(3) C++ Standard Libary 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 ar- rays 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 vari- ables 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 opera- tions (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 ac- cess to the long iword element at the given index (public member function) resizes the private storage if necessary and ac- cess 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 interop- erable [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 immedi- ately 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 oper- ations 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 mask- ing operations generate floating point types using sci- entific 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 alphanu- meric 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 uncon- ditionally 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 opera- tion: 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 in- dicator (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 retroac- tively 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) http://cppreference.com 2024.06.10 std::ios_base(3)
NAME | Synopsis | Member functions | Formatting | Locales | Internal extensible array | Miscellaneous | Member classes | Member types and constants | Deprecated member types | See also
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