std::endl
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<metanoindex/>
<tbody> </tbody>| definiert in Header <ostream>
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template< class CharT, class Traits > std::basic_ostream<charT,traits>& endl( std::basic_ostream<CharT, Traits>& os ); |
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Fügt eine endline Zeichen in der Ausgangsfolge
os und spült es, als ob durch den Aufruf os.put(os.widen('\n')) durch os.flush() gefolgt . Original:
Inserts a endline character into the output sequence
os and flushes it as if by calling os.put(os.widen('\n')) followed by os.flush(). The text has been machine-translated via Google Translate.
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Dies ist ein Nur-Ausgabe-I / O-Manipulators, kann es mit einem Expressionsvektor wie
out << std::endl für jede out vom Typ std::basic_ostream aufgerufen werden .Original:
This is an output-only I/O manipulator, it may be called with an expression such as
out << std::endl for any out of type std::basic_ostream.The text has been machine-translated via Google Translate.
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Notes
Dieser Manipulator verwendet werden, um eine Linie von Ausgang sofort werden, zB bei der Anzeige Ausgang eines lang andauernden Prozesses, Logging-Aktivität von mehreren Threads oder Protokollierung Aktivität eines Programms, das unerwartet abstürzen kann. Eine explizite Flush von std::cout ist auch vor einem Aufruf von std::system erforderlich, wenn die erzeugten Prozess führt alle Bildschirm-I / O (Ein gängiges Beispiel ist
std::system("pause") unter Windows). In den meisten anderen üblichen interaktiven I / O Szenarien ist std::endl überflüssig, wenn mit std::cout verwendet, da jeder Eingang von std::cin, Ausgabe auf std::cerr oder Beendigung des Programms zwingt einen Anruf an std::cout.flush(). Verwendung std::endl statt '\n', von einigen Quellen gefördert werden, erheblich verschlechtern Ausgangsleistung .Original:
This manipulator may be used to produce a line of output immediately, e.g. when displaying output from a long-running process, logging activity of multiple threads or logging activity of a program that may crash unexpectedly. An explicit flush of std::cout is also necessary before a call to std::system, if the spawned process performs any screen I/O (a common example is
std::system("pause") on Windows). In most other usual interactive I/O scenarios, std::endl is redundant when used with std::cout because any input from std::cin, output to std::cerr, or program termination forces a call to std::cout.flush(). Use of std::endl in place of '\n', encouraged by some sources, may significantly degrade output performance.The text has been machine-translated via Google Translate.
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In vielen Implementierungen ist die Standardausgabe line-gepuffert und schriftlich
'\n' verursacht einen Flush sowieso, es sei denn, std::cout.sync_with_stdio(false) ausgeführt wurde. In solchen Situationen unnötige endl nur verschlechtert die Leistung der Datei-Ausgabe, nicht Standard-Ausgabe .Original:
In many implementations, standard output is line-buffered, and writing
'\n' causes a flush anyway, unless std::cout.sync_with_stdio(false) was executed. In those situations, unnecessary endl only degrades the performance of file output, not standard output.The text has been machine-translated via Google Translate.
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Die Codebeispiele in diesem Wiki follow Bjarne Stroustrup in Spülen der Standard-Ausgabe nur wo nötig .
Original:
The code samples on this wiki follow Bjarne Stroustrup in flushing the standard output only where necessary.
The text has been machine-translated via Google Translate.
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Wenn eine unvollständige Zeile der Ausgabe gespült werden muss, kann die std::flush Manipulators verwendet werden .
Original:
When an incomplete line of output needs to be flushed, the std::flush manipulator may be used.
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Wenn jedes Zeichen des Ausgangs gespült werden muss, kann die std::unitbuf Manipulators verwendet werden .
Original:
When every character of output needs to be flushed, the std::unitbuf manipulator may be used.
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Parameter
| os | - | Verweis auf Ausgabe-Stream
Original: reference to output stream The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Rückgabewert
os (Verweis auf den Stream nach Manipulation)Original:
os (reference to the stream after manipulation)The text has been machine-translated via Google Translate.
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Beispiel
Mit \ n statt endl, würde die Ausgabe identisch sein, kann aber nicht in Echtzeit angezeigt .
Original:
With \n instead of endl, the output would be the same, but may not appear in real time.
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#include <iostream>
#include <chrono>
template<typename Diff>
void log_progress(Diff d)
{
std::cout << std::chrono::duration_cast<std::chrono::milliseconds>(d).count()
<< " ms passed" << std::endl;
}
int main()
{
std::cout.sync_with_stdio(false); // on some platforms, stdout flushes on \n
volatile int sink=0;
auto t1 = std::chrono::high_resolution_clock::now();
for(int j=0; j<5; ++j)
{
for(int n=0; n<10000; ++n)
for(int m=0; m<20000; ++m)
sink += m*n; // do some work
auto now = std::chrono::high_resolution_clock::now();
log_progress(now - t1);
}
}
Output:
487 ms passed
974 ms passed
1470 ms passed
1965 ms passed
2455 ms passed
Siehe auch
Kontrollen, ob die Ausgabe nach jeder Operation wird gespült Original: controls whether output is flushed after each operation The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) | |
spült die Ausgabe-Stream Original: flushes the output stream The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktions-Template) | |
synchronisiert mit dem zugrunde liegenden Speicher Original: synchronizes with the underlying storage device The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (öffentliche Elementfunktion of std::basic_ostream)
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