std::basic_ifstream
From cppreference.com
Defined in header <fstream>
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template< class CharT, |
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The class template basic_ifstream
implements high-level input operations on file-based streams. It interfaces a file-based streambuffer (std::basic_filebuf) with the high-level interface of (std::basic_istream).
A typical implementation of std::basic_ifstream
holds only one non-derived data member: an instance of std::basic_filebuf<CharT, Traits>.
Inheritance diagram
Several typedefs for common character types are provided:
Defined in header
<fstream> | |
Type | Definition |
std::ifstream
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std::basic_ifstream<char> |
std::wifstream
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std::basic_ifstream<wchar_t> |
Member types
Member type | Definition |
char_type
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CharT |
traits_type
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Traits ; the program is ill-formed if Traits::char_type is not CharT . |
int_type
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Traits::int_type |
pos_type
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Traits::pos_type |
off_type
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Traits::off_type |
native_handle_type (C++26)
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implementation-defined type that is TriviallyCopyable and semiregular |
Member functions
constructs the file stream (public member function) | |
(destructor) [virtual] (implicitly declared) |
destructs the basic_ifstream and the associated buffer, closes the file (virtual public member function) |
(C++11) |
moves the file stream (public member function) |
(C++11) |
swaps two file streams (public member function) |
returns the underlying raw file device object (public member function) | |
(C++26) |
returns the underlying implementation-defined handle (public member function) |
File operations | |
checks if the stream has an associated file (public member function) | |
opens a file and associates it with the stream (public member function) | |
closes the associated file (public member function) |
Non-member functions
specializes the std::swap algorithm (function template) |
Inherited from std::basic_istream
Member functions
Formatted input | |
extracts formatted data (public member function of std::basic_istream<CharT,Traits> ) | |
Unformatted input | |
extracts characters (public member function of std::basic_istream<CharT,Traits> ) | |
reads the next character without extracting it (public member function of std::basic_istream<CharT,Traits> ) | |
unextracts a character (public member function of std::basic_istream<CharT,Traits> ) | |
puts a character into input stream (public member function of std::basic_istream<CharT,Traits> ) | |
extracts characters until the given character is found (public member function of std::basic_istream<CharT,Traits> ) | |
extracts and discards characters until the given character is found (public member function of std::basic_istream<CharT,Traits> ) | |
extracts blocks of characters (public member function of std::basic_istream<CharT,Traits> ) | |
extracts already available blocks of characters (public member function of std::basic_istream<CharT,Traits> ) | |
returns number of characters extracted by last unformatted input operation (public member function of std::basic_istream<CharT,Traits> ) | |
Positioning | |
returns the input position indicator (public member function of std::basic_istream<CharT,Traits> ) | |
sets the input position indicator (public member function of std::basic_istream<CharT,Traits> ) | |
Miscellaneous | |
synchronizes with the underlying storage device (public member function of std::basic_istream<CharT,Traits> ) |
Member classes
implements basic logic for preparation of the stream for input operations (public member class of std::basic_istream<CharT,Traits> ) |
Inherited from std::basic_ios
Member types
Member type | Definition |
char_type
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CharT
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traits_type
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Traits
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int_type
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Traits::int_type
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pos_type
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Traits::pos_type
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off_type
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Traits::off_type
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Member functions
State functions | |
checks if no error has occurred i.e. I/O operations are available (public member function of std::basic_ios<CharT,Traits> ) | |
checks if end-of-file has been reached (public member function of std::basic_ios<CharT,Traits> ) | |
checks if an error has occurred (public member function of std::basic_ios<CharT,Traits> ) | |
checks if a non-recoverable error has occurred (public member function of std::basic_ios<CharT,Traits> ) | |
checks if an error has occurred (synonym of fail()) (public member function of std::basic_ios<CharT,Traits> ) | |
checks if no error has occurred (synonym of ! fail()) (public member function of std::basic_ios<CharT,Traits> ) | |
returns state flags (public member function of std::basic_ios<CharT,Traits> ) | |
sets state flags (public member function of std::basic_ios<CharT,Traits> ) | |
modifies state flags (public member function of std::basic_ios<CharT,Traits> ) | |
Formatting | |
copies formatting information (public member function of std::basic_ios<CharT,Traits> ) | |
manages the fill character (public member function of std::basic_ios<CharT,Traits> ) | |
Miscellaneous | |
manages exception mask (public member function of std::basic_ios<CharT,Traits> ) | |
sets the locale (public member function of std::basic_ios<CharT,Traits> ) | |
manages associated stream buffer (public member function of std::basic_ios<CharT,Traits> ) | |
manages tied stream (public member function of std::basic_ios<CharT,Traits> ) | |
narrows characters (public member function of std::basic_ios<CharT,Traits> ) | |
widens characters (public member function of std::basic_ios<CharT,Traits> ) |
Inherited from std::ios_base
Member functions
Formatting | |
manages format flags (public member function of std::ios_base ) | |
sets specific format flag (public member function of std::ios_base ) | |
clears specific format flag (public member function of std::ios_base ) | |
manages decimal precision of floating point operations (public member function of std::ios_base ) | |
manages field width (public member function of std::ios_base ) | |
Locales | |
sets locale (public member function of std::ios_base ) | |
returns current locale (public member function of std::ios_base ) | |
Internal extensible array | |
[static] |
returns a program-wide unique integer that is safe to use as index to pword() and iword() (public static member function of std::ios_base ) |
resizes the private storage if necessary and access to the long element at the given index (public member function of std::ios_base ) | |
resizes the private storage if necessary and access to the void* element at the given index (public member function of std::ios_base ) | |
Miscellaneous | |
registers event callback function (public member function of std::ios_base ) | |
[static] |
sets whether C++ and C I/O libraries are interoperable (public static member function of std::ios_base ) |
Member classes | |
stream exception (public member class of std::ios_base ) | |
initializes standard stream objects (public member class of std::ios_base ) |
Member types and constants | |||||||||||||||||||||||||||||||||||||||
Type | Explanation | ||||||||||||||||||||||||||||||||||||||
stream open mode type
The following constants are also defined:
(typedef) | |||||||||||||||||||||||||||||||||||||||
formatting flags type
The following constants are also defined:
(typedef) | |||||||||||||||||||||||||||||||||||||||
state of the stream type
The following constants are also defined:
(typedef) | |||||||||||||||||||||||||||||||||||||||
seeking direction type
The following constants are also defined:
(typedef) | |||||||||||||||||||||||||||||||||||||||
specifies event type (enum) | |||||||||||||||||||||||||||||||||||||||
callback function type (typedef) |
Notes
Feature-test macro | Value | Std | Feature |
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__cpp_lib_fstream_native_handle |
202306L | (C++26) | native handles support |
Example
Run this code
#include <fstream> #include <iostream> #include <string> int main() { std::string filename = "Test.b"; // prepare a file to read double d = 3.14; std::ofstream(filename, std::ios::binary) .write(reinterpret_cast<char*>(&d), sizeof d) << 123 << "abc"; // open file for reading std::ifstream istrm(filename, std::ios::binary); if (!istrm.is_open()) std::cout << "failed to open " << filename << '\n'; else { double d; istrm.read(reinterpret_cast<char*>(&d), sizeof d); // binary input int n; std::string s; if (istrm >> n >> s) // text input std::cout << "read back from file: " << d << ' ' << n << ' ' << s << '\n'; } }
Output:
read back from file: 3.14 123 abc