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Synchronizes the associated stream buffer with its controlled output sequence.
For stream buffer objects that implement intermediate buffers, this function requests all characters to be written to the controlled sequence.
Its behavior is equivalent to calling os's member function flush.
A member function with the same name and behavior exists (see ostream::flush).
Errors are signaled by modifying the internal state flags of os:
Multiple flags may be set on os by a single operation.
If the operation sets an internal state flag of os that was registered using its member exceptions, the function throws an exception of type ios_base::failure.
This program requests
Concurrent access to the same stream object may cause data races, except for the standard stream objects (cout, cerr, clog, wcout, wcerr and wclog) when these are synchronized with stdio (in this case, no data races are initiated, although no guarantees are given on the order in which characters from multiple threads are inserted).
It throws an exception of member type failure if the resulting error state flag of os is not goodbit and member exceptions was set to throw for that state.
Any exception thrown by an internal operation is caught and handled by the function, setting os's badbit. If badbit was set on the last call to exceptions for os, the function rethrows the caught exception.
Reference
C library:
- <cassert> (assert.h)
- <cctype> (ctype.h)
- <cerrno> (errno.h)
-
<cfenv> (fenv.h)C++11
- <cfloat> (float.h)
-
<cinttypes> (inttypes.h)C++11
- <ciso646> (iso646.h)
- <climits> (limits.h)
- <clocale> (locale.h)
- <cmath> (math.h)
- <csetjmp> (setjmp.h)
- <csignal> (signal.h)
- <cstdarg> (stdarg.h)
-
<cstdbool> (stdbool.h)C++11
- <cstddef> (stddef.h)
-
<cstdint> (stdint.h)C++11
- <cstdio> (stdio.h)
- <cstdlib> (stdlib.h)
- <cstring> (string.h)
-
<ctgmath> (tgmath.h)C++11
- <ctime> (time.h)
-
<cuchar> (uchar.h)C++11
- <cwchar> (wchar.h)
- <cwctype> (wctype.h)
Containers:
-
<array>C++11
- <deque>
-
<forward_list>C++11
- <list>
- <map>
- <queue>
- <set>
- <stack>
-
<unordered_map>C++11
-
<unordered_set>C++11
- <vector>
-
Input/Output:
Multi-threading:
-
<atomic>C++11
-
<condition_variable>C++11
-
<future>C++11
-
<mutex>C++11
-
<thread>C++11
-
Other:
- <algorithm>
- <bitset>
-
<chrono>C++11
-
<codecvt>C++11
- <complex>
- <exception>
- <functional>
-
<initializer_list>C++11
- <iterator>
- <limits>
- <locale>
- <memory>
- <new>
- <numeric>
-
<random>C++11
-
<ratio>C++11
-
<regex>C++11
- <stdexcept>
- <string>
-
<system_error>C++11
-
<tuple>C++11
-
<type_traits>C++11
-
<typeindex>C++11
- <typeinfo>
- <utility>
- <valarray>
function
<ostream> <iostream>
std::flush
| for ostream | ostream& flush (ostream& os); |
|---|---|
| basic template | template <class charT, class traits>basic_ostream<charT,traits>& flush (basic_ostream<charT,traits>& os); |
Flush stream buffer
For stream buffer objects that implement intermediate buffers, this function requests all characters to be written to the controlled sequence.
Its behavior is equivalent to calling os's member function flush.
A member function with the same name and behavior exists (see ostream::flush).
Parameters
- os
- Output stream object affected.
Because this function is a manipulator, it is designed to be used alone with no arguments in conjunction with the insertion (<<) operations on output streams (see example below).
Return Value
Argument os.Errors are signaled by modifying the internal state flags of os:
| flag | error |
|---|---|
| eofbit | - |
| failbit | May be set if the construction of a sentry object failed. |
| badbit | The synchronization operation failed (including if the function catches an exception thrown by an internal operation). When set, the integrity of the stream may have been affected. |
If the operation sets an internal state flag of os that was registered using its member exceptions, the function throws an exception of type ios_base::failure.
Example
|
|
This program requests
test.txt to be flushed 100 times.Data races
Modifies os.Concurrent access to the same stream object may cause data races, except for the standard stream objects (cout, cerr, clog, wcout, wcerr and wclog) when these are synchronized with stdio (in this case, no data races are initiated, although no guarantees are given on the order in which characters from multiple threads are inserted).
Exception safety
Basic guarantee: if an exception is thrown, os is in a valid state.It throws an exception of member type failure if the resulting error state flag of os is not goodbit and member exceptions was set to throw for that state.
Any exception thrown by an internal operation is caught and handled by the function, setting os's badbit. If badbit was set on the last call to exceptions for os, the function rethrows the caught exception.
See also
- endl
- Insert newline and flush (function)
- ostream::flush
- Flush output stream buffer (public member function)
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Spotted an error? contact us