std::cin, std::wcin

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Input/output library

I/O manipulators

Print functions (C++23)

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

basic_spanbuf (C++23)

strstreambuf (C++98/26*)

basic_syncbuf (C++20)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

basic_ispanstream (C++23)

basic_ospanstream (C++23)

basic_spanstream (C++23)

istrstream (C++98/26*)

ostrstream (C++98/26*)

strstream (C++98/26*)

Synchronized Output

basic_osyncstream (C++20)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

std::basic_istream

Global objects

cinwcin

Member functions

basic_istream::basic_istream

basic_istream::~basic_istream

basic_istream::operator= (C++11)

Formatted input

basic_istream::operator>>

Unformatted input

basic_istream::get

basic_istream::peek

basic_istream::unget

basic_istream::putback

basic_istream::getline

basic_istream::ignore

basic_istream::read

basic_istream::readsome

basic_istream::gcount

Positioning

basic_istream::tellg

basic_istream::seekg

Miscellaneous

basic_istream::sync

basic_istream::swap (C++11)

Member classes

basic_istream::sentry

Non-member functions

operator>>(std::basic_istream)

 

Defined in header <iostream>
extern std::istream cin;	(1)
extern std::wistream wcin;	(2)

The global objects std::cin and std::wcin control input from a stream buffer of implementation-defined type (derived from std::streambuf), associated with the standard C input stream stdin.

These objects are guaranteed to be initialized during or before the first time an object of type std::ios_base::Init is constructed and are available for use in the constructors and destructors of static objects with ordered initialization (as long as <iostream> is included before the object is defined).

Unless sync_with_stdio(false) has been issued, it is safe to concurrently access these objects from multiple threads for both formatted and unformatted input.

Once initialized:

1) std::cin.tie() returns &std::cout. This means that any input operation on std::cin forces a call to std::cout.flush() if any characters are pending for output..

2) std::wcin.tie() returns &std::wcout. This means that any input operation on std::wcin forces a call to std::wcout.flush() if any characters are pending for output.

Notes

The “c” in the name refers to “character” (stroustrup.com FAQ); cin means “character input” and wcin means “wide character input”.

Example

Run this code

#include <iostream>
 
struct Foo
{
    int n;
    Foo()
    {
        std::cout << "Enter n: "; / no flush needed
        std::cin >> n;
    }
};
 
Foo f; / static object
 
int main()
{
    std::cout << "f.n is " << f.n << '\n';
}

Possible output:

Enter n: 10
f.n is 10

See also

Init	initializes standard stream objects (public member class of std::ios_base)
coutwcout	writes to the standard C output stream stdout (global object)
stdinstdoutstderr	expression of type FILE* associated with the input stream expression of type FILE* associated with the output stream expression of type FILE* associated with the error output stream (macro constant)

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