Namespaces
Variants
Views
Actions

Standard library header <iostream>

From cppreference.com
< cpp‎ | header
 
 
Standard library headers
Language support
Concepts
<concepts> (C++20)
Diagnostics
<system_error> (C++11)

Memory management
<memory_resource> (C++17)  
Metaprogramming
<type_traits> (C++11)
<ratio> (C++11)
General utilities
<utility>
<tuple> (C++11)
<optional> (C++17)
<variant> (C++17)
<any> (C++17)
<debugging> (C++26)
<expected> (C++23)
<bitset>
<charconv> (C++17)
<format> (C++20)
<bit> (C++20)

Strings
<cuchar> (C++11)

Containers
<flat_set> (C++23)
<span> (C++20)
<mdspan> (C++23)

Iterators
<iterator>
Ranges
<ranges> (C++20)
<generator> (C++23)
Algorithms
Numerics
<cfenv> (C++11)
<complex>
<cmath>
<linalg> (C++26)
<numbers> (C++20)

Time
<chrono> (C++11)
Localization
<codecvt> (C++11/17/26*)
<text_encoding> (C++26)
Input/output
<filesystem> (C++17)
<cstdio>
<cinttypes> (C++11)
<strstream> (C++98*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20)
<thread> (C++11)
<atomic> (C++11)
<rcu> (C++26)
<stdatomic.h> (C++23)
<mutex> (C++11)
<shared_mutex> (C++14)

<condition_variable> (C++11)  
<semaphore> (C++20)
<latch> (C++20)

<barrier> (C++20)
<future> (C++11)
<hazard_pointer> (C++26)

C compatibility
<cstdbool> (C++11/17/20*)  
<ccomplex> (C++11/17/20*)
<ctgmath> (C++11/17/20*)

<cstdalign> (C++11/17/20*)

<ciso646> (until C++20)

 

This header is part of the Input/output library.

Including <iostream> behaves as if it defines a static storage duration object of type std::ios_base::Init, whose constructor initializes the standard stream objects if it is the first std::ios_base::Init object to be constructed, and whose destructor flushes those objects (except for cin and wcin) if it is the last std::ios_base::Init object to be destroyed.

Contents

Includes

(C++11)
std::ios_base class, std::basic_ios class template and several typedefs[edit]
std::basic_streambuf class template[edit]
(C++11)
std::basic_istream class template and several typedefs[edit]
(C++11)
std::basic_ostream, std::basic_iostream class templates and several typedefs[edit]

Objects

reads from the standard C input stream stdin
(global object)[edit]
writes to the standard C output stream stdout
(global object)[edit]
writes to the standard C error stream stderr, unbuffered
(global object)[edit]
writes to the standard C error stream stderr
(global object)[edit]

[edit] Synopsis

#include <ios>
#include <streambuf>
#include <istream>
#include <ostream>
 
namespace std {
  extern istream cin;
  extern ostream cout;
  extern ostream cerr;
  extern ostream clog;
 
  extern wistream wcin;
  extern wostream wcout;
  extern wostream wcerr;
  extern wostream wclog;
}

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 155 C++98 the type of the static object was std::basic_ios::Init
(not strictly wrong, but the wording was misleading)
corrected to std::ios_base::Init
LWG 1123 C++98 including <iostream> did not guarantee the
construction of std::ios_base::Init objects
guarantees