Standard library header <fstream>

C++

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Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Standard Library header files

Language Support
<cstddef> <limits> <climits> <contract>	<cfloat> <cstdint> <new> <version>	<typeinfo> <exception> <initializer_list>	<csignal> <csetjmp> <cstdarg>
Concepts
<concepts>
Diagnostics
<stdexcept>	<cassert>	<cerrno>	<system_error>
General utilities
<utility> <memory> <memory_resource> <scoped_allocator> <compare>	<bitset> <tuple> <optional> <any> <variant>	<type_traits> <ratio> <chrono> <typeindex> <functional>	<ctime> <cstdlib>
Strings
<string> <string_view>	<cctype> <cwctype>	<cwchar> <cuchar>	<cstring> <charconv>
Localization
<locale>	<codecvt>	<clocale>
Containers
<span> <array> <vector>	<deque> <forward_list> <list>	<map> <set> <queue>	<unordered_map> <unordered_set> <stack>
Iterators
<iterator>
Algorithms
<algorithm>	<execution>
Numerics
<complex> <random>	<valarray> <numeric>	<cfenv> <cmath>	<bit>
Input/Output
<iosfwd> <ios> <iomanip> <streambuf>	<istream> <ostream> <iostream>	<sstream> <fstream> <syncstream>	<cstdio> <cinttypes> <strstream>
Regular expressions
<regex>
Filesystem support
<filesystem>
Thread support
<thread> <atomic>	<mutex> <shared_mutex>	<condition_variable> <future>
C compatibility
<ciso646> <cstdalign>	<cstdbool> <ccomplex>	<ctgmath>

This header is part of the Input/Output library.

Classes
basic_filebuf	implements raw file device (class template)
basic_ifstream	implements high-level file stream input operations (class template)
basic_ofstream	implements high-level file stream output operations (class template)
basic_fstream	implements high-level file stream input/output (class template)
Typedefs
filebuf	basic_filebuf<char>
wfilebuf	basic_filebuf<wchar_t>
ifstream	basic_ifstream<char>
wifstream	basic_ifstream<wchar_t>
ofstream	basic_ofstream<char>
wofstream	basic_ofstream<wchar_t>
fstream	basic_fstream<char>
wfstream	basic_fstream<wchar_t>
Functions
std::swap(std::basic_filebuf) (C++11)	specializes the std::swap algorithm (function template)
std::swap(std::basic_ifstream) (C++11)	specializes the std::swap algorithm (function template)
std::swap(std::basic_ofstream) (C++11)	specializes the std::swap algorithm (function template)
std::swap(std::basic_fstream) (C++11)	specializes the std::swap algorithm (function template)

Synopsis

namespace std {

template <class charT, class traits = char_traits<charT> >
    class basic_filebuf;
typedef basic_filebuf<char> filebuf;
typedef basic_filebuf<wchar_t> wfilebuf;
template <class charT, class traits>
    void swap(basic_filebuf<charT, traits>& x,
              basic_filebuf<charT, traits>& y);

template <class charT, class traits = char_traits<charT> >
    class basic_ifstream;
typedef basic_ifstream<char> ifstream;
typedef basic_ifstream<wchar_t> wifstream;
template <class charT, class traits>
    void swap(basic_ifstream<charT, traits>& x,
              basic_ifstream<charT, traits>& y);

template <class charT, class traits = char_traits<charT> >
    class basic_ofstream;
typedef basic_ofstream<char> ofstream;
typedef basic_ofstream<wchar_t> wofstream;
template <class charT, class traits>
    void swap(basic_ofstream<charT, traits>& x,
              basic_ofstream<charT, traits>& y);

template <class charT, class traits = char_traits<charT> >
    class basic_fstream;
typedef basic_fstream<char> fstream;
typedef basic_fstream<wchar_t> wfstream;
template <class charT, class traits>
    void swap(basic_fstream<charT, traits>& x,
              basic_fstream<charT, traits>& y);
}

Class std::basic_filebuf

template <class charT, class traits = char_traits<charT> >
class basic_filebuf : public basic_streambuf<charT,traits> {
 public:
    typedef charT char_type;
    typedef typename traits::int_type int_type;
    typedef typename traits::pos_type pos_type;
    typedef typename traits::off_type off_type;
    typedef traits traits_type;

    // Constructors/destructor:
    basic_filebuf();
    basic_filebuf(const basic_filebuf& rhs) = delete;
    basic_filebuf(basic_filebuf&& rhs);
    virtual ~basic_filebuf();

    // Assign/swap:
    basic_filebuf& operator=(const basic_filebuf& rhs) = delete;
    basic_filebuf& operator=(basic_filebuf&& rhs);
    void swap(basic_filebuf& rhs);

    // Members:
    bool is_open() const;
    basic_filebuf<charT,traits>* open(const char* s, ios_base::openmode mode);
    basic_filebuf<charT,traits>* open(const string& s, ios_base::openmode mode);
    basic_filebuf<charT,traits>* close();

 protected:
    // Overridden virtual functions:
    virtual streamsize showmanyc();
    virtual int_type underflow();
    virtual int_type uflow();
    virtual int_type pbackfail(int_type c = traits::eof());
    virtual int_type overflow (int_type c = traits::eof());
    virtual basic_streambuf<charT,traits>* setbuf(char_type* s, streamsize n);
    virtual pos_type seekoff(off_type off, ios_base::seekdir way,
                             ios_base::openmode which = ios_base::in|ios_base::out);
    virtual pos_type seekpos(pos_type sp,
                             ios_base::openmode which = ios_base::in|ios_base::out);
    virtual int sync();
    virtual void imbue(const locale& loc);
};

Class std::basic_ifstream

template <class charT, class traits = char_traits<charT> >
class basic_ifstream : public basic_istream<charT,traits> {
 public:
    typedef charT char_type;
    typedef typename traits::int_type int_type;
    typedef typename traits::pos_type pos_type;
    typedef typename traits::off_type off_type;
    typedef traits traits_type;

    // Constructors:
    basic_ifstream();
    explicit basic_ifstream(const char* s, ios_base::openmode mode = ios_base::in);
    explicit basic_ifstream(const string& s, ios_base::openmode mode = ios_base::in);
    basic_ifstream(const basic_ifstream& rhs) = delete;
    basic_ifstream(basic_ifstream&& rhs);

    // Assign/swap:
    basic_ifstream& operator=(const basic_ifstream& rhs) = delete;
    basic_ifstream& operator=(basic_ifstream&& rhs);
    void swap(basic_ifstream& rhs);

    // Members:
    basic_filebuf<charT,traits>* rdbuf() const;
    bool is_open() const;
    void open(const char* s, ios_base::openmode mode = ios_base::in);
    void open(const string& s, ios_base::openmode mode = ios_base::in);
    void close();

 private:
    basic_filebuf<charT,traits> sb; // exposition only
};

Class std::basic_ofstream

template <class charT, class traits = char_traits<charT> >
class basic_ofstream : public basic_ostream<charT,traits> {
 public:
    typedef charT char_type;
    typedef typename traits::int_type int_type;
    typedef typename traits::pos_type pos_type;
    typedef typename traits::off_type off_type;
    typedef traits traits_type;

    // Constructors:
    basic_ofstream();
    explicit basic_ofstream(const char* s, ios_base::openmode mode = ios_base::out);
    explicit basic_ofstream(const string& s, ios_base::openmode mode = ios_base::out);
    basic_ofstream(const basic_ofstream& rhs) = delete;
    basic_ofstream(basic_ofstream&& rhs);

    // Assign/swap:
    basic_ofstream& operator=(const basic_ofstream& rhs) = delete;
    basic_ofstream& operator=(basic_ofstream&& rhs);
    void swap(basic_ofstream& rhs);

    // Members:
    basic_filebuf<charT,traits>* rdbuf() const;
    bool is_open() const;
    void open(const char* s, ios_base::openmode mode = ios_base::out);
    void open(const string& s, ios_base::openmode mode = ios_base::out);
    void close();

 private:
    basic_filebuf<charT,traits> sb; // exposition only
};

Class std::basic_fstream

template <class charT, class traits=char_traits<charT> >
class basic_fstream : public basic_iostream<charT,traits> {
 public:
    typedef charT char_type;
    typedef typename traits::int_type int_type;
    typedef typename traits::pos_type pos_type;
    typedef typename traits::off_type off_type;
    typedef traits traits_type;

    // constructors/destructor
    basic_fstream();
    explicit basic_fstream(const char* s,
                           ios_base::openmode mode = ios_base::in|ios_base::out);
    explicit basic_fstream(const string& s,
                           ios_base::openmode mode = ios_base::in|ios_base::out);
    basic_fstream(const basic_fstream& rhs) = delete;
    basic_fstream(basic_fstream&& rhs);

    // Assign/swap:
    basic_fstream& operator=(const basic_fstream& rhs) = delete;
    basic_fstream& operator=(basic_fstream&& rhs);
    void swap(basic_fstream& rhs);

    // Members:
    basic_filebuf<charT,traits>* rdbuf() const;
    bool is_open() const;
    void open(const char* s,
              ios_base::openmode mode = ios_base::in|ios_base::out);
    void open(const string& s,
              ios_base::openmode mode = ios_base::in|ios_base::out);
    void close();

 private:
    basic_filebuf<charT,traits> sb; // exposition only
};