[ifstream.cons]

# 31 Input/output library [[input.output]](./#input.output)

## 31.10 File-based streams [[file.streams]](file.streams#ifstream.cons)

### 31.10.4 Class template basic_ifstream [[ifstream]](ifstream#cons)

#### 31.10.4.2 Constructors [ifstream.cons]

[ð](#lib:basic_ifstream,constructor)

`basic_ifstream();
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L11843)

*Effects*: Initializes the base class withbasic_istream<charT, traits>(addressof(*sb*)) ([[istream.cons]](istream.cons "31.7.5.2.2 Constructors"))
and *sb* withbasic_filebuf<charT, traits>() ([[filebuf.cons]](filebuf.cons "31.10.3.2 Constructors"))[.](#1.sentence-1)

[ð](#lib:basic_ifstream,constructor_)

`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; see [[fstream.syn]](fstream.syn "31.10.1 Header <fstream> synopsis")
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L11860)

*Effects*: Initializes the base class withbasic_istream<charT, traits>(addressof(*sb*)) ([[istream.cons]](istream.cons "31.7.5.2.2 Constructors"))
and *sb* withbasic_filebuf<charT, traits>() ([[filebuf.cons]](filebuf.cons "31.10.3.2 Constructors")),
then callsrdbuf()->open(s, mode | ios_base​::​in)[.](#2.sentence-1)

If that function returns a null pointer, callssetstate(failbit)[.](#2.sentence-2)

[ð](#lib:basic_ifstream,constructor__)

`explicit basic_ifstream(const string& s,
                        ios_base::openmode mode = ios_base::in);
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L11879)

*Effects*: Equivalent to basic_ifstream(s.c_str(), mode)[.](#3.sentence-1)

[ð](#lib:basic_ifstream,constructor___)

`template<class T>
  explicit basic_ifstream(const T& s, ios_base::openmode mode = ios_base::in);
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L11891)

*Constraints*: is_same_v<T, filesystem​::​path> is true[.](#4.sentence-1)

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L11895)

*Effects*: Equivalent to basic_ifstream(s.c_str(), mode)[.](#5.sentence-1)

[ð](#lib:basic_ifstream,constructor____)

`basic_ifstream(basic_ifstream&& rhs);
`

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L11906)

*Effects*: Move constructs the base class, and the contained basic_filebuf[.](#6.sentence-1)

Then calls basic_istream<charT, traits>​::​set_rdbuf(​addressof(*sb*)) to install the contained basic_filebuf[.](#6.sentence-2)
