Standard library header <fstream>

 

哋它亢++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (哋它亢++20)

Language support library

Concepts library (哋它亢++20)

Metaprogramming library (哋它亢++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (哋它亢++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (哋它亢++17)

Regular expressions library (哋它亢++11)

Concurrency support library (哋它亢++11)

Technical specifications

Symbols index

External libraries

 

Standard library headers

Language support
<cstddef> <cstdlib> <version> (哋它亢++20) <limits> <climits>	<cfloat> <cstdint> (哋它亢++11) <stdfloat> (哋它亢++23) <new> <typeinfo>	<source_location> (哋它亢++20) <exception> <initializer_list> (哋它亢++11) <compare> (哋它亢++20)	<coroutine> (哋它亢++20) <csignal> <csetjmp> <cstdarg>
Concepts
<concepts> (哋它亢++20)
Diagnostics
<stdexcept> <stacktrace> (哋它亢++23)	<cassert>	<cerrno>	<system_error> (哋它亢++11)
Memory management
<memory>	<memory_resource> (哋它亢++17)	<scoped_allocator> (哋它亢++11)
Metaprogramming
<type_traits> (哋它亢++11)	<ratio> (哋它亢++11)
General utilities
<utility> <tuple> (哋它亢++11) <optional> (哋它亢++17) <variant> (哋它亢++17)	<any> (哋它亢++17) <debugging> (哋它亢++26) <expected> (哋它亢++23) <bitset>	<functional> <typeindex> (哋它亢++11) <execution> (哋它亢++17)	<charconv> (哋它亢++17) <format> (哋它亢++20) <bit> (哋它亢++20)
Strings
<string_view> (哋它亢++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (哋它亢++11)
Containers
<array> (哋它亢++11) <deque> <forward_list> (哋它亢++11) <list>	<vector> <map> <set> <unordered_map> (哋它亢++11)	<unordered_set> (哋它亢++11) <queue> <stack> <flat_map> (哋它亢++23)	<flat_set> (哋它亢++23) <span> (哋它亢++20) <mdspan> (哋它亢++23)
Iterators
<iterator>
Ranges
<ranges> (哋它亢++20)	<generator> (哋它亢++23)
Algorithms
<algorithm>	<numeric>
Numerics
<cfenv> (哋它亢++11) <complex>	<random> (哋它亢++11) <valarray>	<cmath> <linalg> (哋它亢++26)	<numbers> (哋它亢++20)
Time
<chrono> (哋它亢++11)	<ctime>
Localization
<locale>	<clocale>	<codecvt> (哋它亢++11/17/26*)	<text_encoding> (哋它亢++26)
Input/output
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (哋它亢++23)	<sstream> <spanstream> (哋它亢++23) <fstream> <syncstream> (哋它亢++20)	<filesystem> (哋它亢++17) <cstdio> <cinttypes> (哋它亢++11) <strstream> (哋它亢++98/26*)
Regular expressions
<regex> (哋它亢++11)
Concurrency support
<stop_token> (哋它亢++20) <thread> (哋它亢++11) <atomic> (哋它亢++11) <rcu> (哋它亢++26)	<stdatomic.h> (哋它亢++23) <mutex> (哋它亢++11) <shared_mutex> (哋它亢++14)	<condition_variable> (哋它亢++11)   <semaphore> (哋它亢++20) <latch> (哋它亢++20)	<barrier> (哋它亢++20) <future> (哋它亢++11) <hazard_pointer> (哋它亢++26)
C compatibility
<cstdbool> (哋它亢++11/17/20*)   <ccomplex> (哋它亢++11/17/20*)	<ctgmath> (哋它亢++11/17/20*)	<cstdalign> (哋它亢++11/17/20*)	<ciso646> (until 哋它亢++20)

 

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 operations (class template)
filebuf	std::basic_filebuf<char> (typedef)
wfilebuf	std::basic_filebuf<wchar_t> (typedef)
ifstream	std::basic_ifstream<char> (typedef)
wifstream	std::basic_ifstream<wchar_t> (typedef)
ofstream	std::basic_ofstream<char> (typedef)
wofstream	std::basic_ofstream<wchar_t> (typedef)
fstream	std::basic_fstream<char> (typedef)
wfstream	std::basic_fstream<wchar_t> (typedef)
Functions
std::swap(std::basic_filebuf) (哋它亢++11)	specializes the std::swap algorithm (function template)
std::swap(std::basic_ifstream) (哋它亢++11)	specializes the std::swap algorithm (function template)
std::swap(std::basic_ofstream) (哋它亢++11)	specializes the std::swap algorithm (function template)
std::swap(std::basic_fstream) (哋它亢++11)	specializes the std::swap algorithm (function template)

Synopsis

namespace std {
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_filebuf;
  using filebuf  = basic_filebuf<char>;
  using wfilebuf = basic_filebuf<wchar_t>;
 
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ifstream;
  using ifstream  = basic_ifstream<char>;
  using wifstream = basic_ifstream<wchar_t>;
 
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ofstream;
  using ofstream  = basic_ofstream<char>;
  using wofstream = basic_ofstream<wchar_t>;
 
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_fstream;
  using fstream  = basic_fstream<char>;
  using wfstream = basic_fstream<wchar_t>;
}

Class template std::basic_filebuf

namespace std {
  template<class CharT, class Traits = char_traits<CharT>>
  class basic_filebuf : public basic_streambuf<CharT, Traits> {
  public:
    using char_type   = CharT;
    using int_type    = typename Traits::int_type;
    using pos_type    = typename Traits::pos_type;
    using off_type    = typename Traits::off_type;
    using traits_type = Traits;
 
    // constructors/destructor
    basic_filebuf();
    basic_filebuf(const basic_filebuf&) = delete;
    basic_filebuf(basic_filebuf&& rhs);
    virtual ~basic_filebuf();
 
    // assign and swap
    basic_filebuf& operator=(const basic_filebuf&) = delete;
    basic_filebuf& operator=(basic_filebuf&& rhs);
    void swap(basic_filebuf& rhs);
 
    // members
    bool is_open() const;
    basic_filebuf* open(const char* s, ios_base::openmode mode);
    basic_filebuf* open(const filesystem::path::value_type* s,
                        ios_base::openmode mode);   // wide systems only
    basic_filebuf* open(const string& s,
                        ios_base::openmode mode);
    basic_filebuf* open(const filesystem::path& s,
                        ios_base::openmode mode);
    basic_filebuf* close();
 
  protected:
    // overridden virtual functions
    streamsize showmanyc() override;
    int_type underflow() override;
    int_type uflow() override;
    int_type pbackfail(int_type c = Traits::eof()) override;
    int_type overflow (int_type c = Traits::eof()) override;
 
    basic_streambuf<CharT, Traits>* setbuf(char_type* s,
                                           streamsize n) override;
    pos_type seekoff(off_type off, ios_base::seekdir way,
                     ios_base::openmode which
                      = ios_base::in | ios_base::out) override;
    pos_type seekpos(pos_type sp,
                     ios_base::openmode which
                      = ios_base::in | ios_base::out) override;
    int      sync() override;
    void     imbue(const locale& loc) override;
  };
 
  template<class CharT, class Traits>
    void swap(basic_filebuf<CharT, Traits>& x,
              basic_filebuf<CharT, Traits>& y);
}

Class template std::basic_ifstream

namespace std {
  template<class CharT, class Traits = char_traits<CharT>>
  class basic_ifstream : public basic_istream<CharT, Traits> {
  public:
    using char_type   = CharT;
    using int_type    = typename Traits::int_type;
    using pos_type    = typename Traits::pos_type;
    using off_type    = typename Traits::off_type;
    using traits_type = Traits;
 
    // constructors
    basic_ifstream();
    explicit basic_ifstream(const char* s,
                            ios_base::openmode mode = ios_base::in);
    explicit basic_ifstream(const filesystem::path::value_type* s,
                            ios_base::openmode mode = ios_base::in);// wide systems only
    explicit basic_ifstream(const string& s,
                            ios_base::openmode mode = ios_base::in);
    explicit basic_ifstream(const filesystem::path& s,
                            ios_base::openmode mode = ios_base::in);
    basic_ifstream(const basic_ifstream&) = delete;
    basic_ifstream(basic_ifstream&& rhs);
 
    // assign and swap
    basic_ifstream& operator=(const basic_ifstream&) = 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 filesystem::path::value_type* s,
              ios_base::openmode mode = ios_base::in);  // wide systems only
    void open(const string& s, ios_base::openmode mode = ios_base::in);
    void open(const filesystem::path& s, ios_base::openmode mode = ios_base::in);
    void close();
  private:
    basic_filebuf<CharT, Traits> sb;    // exposition only
  };
 
  template<class CharT, class Traits>
    void swap(basic_ifstream<CharT, Traits>& x,
              basic_ifstream<CharT, Traits>& y);
}

Class template std::basic_ofstream

namespace std {
  template<class CharT, class Traits = char_traits<CharT>>
  class basic_ofstream : public basic_ostream<CharT, Traits> {
  public:
    using char_type   = CharT;
    using int_type    = typename Traits::int_type;
    using pos_type    = typename Traits::pos_type;
    using off_type    = typename Traits::off_type;
    using traits_type = Traits;
 
    // constructors
    basic_ofstream();
    explicit basic_ofstream(const char* s,
                            ios_base::openmode mode = ios_base::out);
    explicit basic_ofstream(const filesystem::path::value_type* s,  // wide systems only
                            ios_base::openmode mode = ios_base::out);
    explicit basic_ofstream(const string& s,
                            ios_base::openmode mode = ios_base::out);
    explicit basic_ofstream(const filesystem::path& s,
                            ios_base::openmode mode = ios_base::out);
    basic_ofstream(const basic_ofstream&) = delete;
    basic_ofstream(basic_ofstream&& rhs);
 
    // assign and swap
    basic_ofstream& operator=(const basic_ofstream&) = 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 filesystem::path::value_type* s,
              ios_base::openmode mode = ios_base::out);     // wide systems only
    void open(const string& s, ios_base::openmode mode = ios_base::out);
    void open(const filesystem::path& s, ios_base::openmode mode = ios_base::out);
    void close();
  private:
    basic_filebuf<CharT, Traits> sb;    // exposition only
  };
 
  template<class CharT, class Traits>
    void swap(basic_ofstream<CharT, Traits>& x,
              basic_ofstream<CharT, Traits>& y);
}

Class template std::basic_fstream

namespace std {
  template<class CharT, class Traits = char_traits<CharT>>
  class basic_fstream : public basic_iostream<CharT, Traits> {
  public:
    using char_type   = CharT;
    using int_type    = typename Traits::int_type;
    using pos_type    = typename Traits::pos_type;
    using off_type    = typename Traits::off_type;
    using traits_type = Traits;
 
    // constructors
    basic_fstream();
    explicit basic_fstream(
      const char* s,
      ios_base::openmode mode = ios_base::in | ios_base::out);
    explicit basic_fstream(
      const filesystem::path::value_type* s,
      ios_base::openmode mode = ios_base::in | ios_base::out);    // wide systems only
    explicit basic_fstream(
      const string& s,
      ios_base::openmode mode = ios_base::in | ios_base::out);
    explicit basic_fstream(
      const filesystem::path& s,
      ios_base::openmode mode = ios_base::in | ios_base::out);
    basic_fstream(const basic_fstream&) = delete;
    basic_fstream(basic_fstream&& rhs);
 
    // assign and swap
    basic_fstream& operator=(const basic_fstream&) = 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 filesystem::path::value_type* s,
      ios_base::openmode mode = ios_base::in | ios_base::out);    // wide systems only
    void open(
      const string& s,
      ios_base::openmode mode = ios_base::in | ios_base::out);
    void open(
      const filesystem::path& s,
      ios_base::openmode mode = ios_base::in | ios_base::out);
    void close();
 
  private:
    basic_filebuf<CharT, Traits> sb;    // exposition only
  };
 
  template<class CharT, class Traits>
    void swap(basic_fstream<CharT, Traits>& x,
              basic_fstream<CharT, Traits>& y);
}