std::endl
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<tbody> </tbody>| Definido no cabeçalho <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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Insere um caractere de fim de linha para o
os seqüência de saída e libera-lo como se chamando os.put(os.widen('\n')) seguido por os.flush(). 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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Esta é uma saída de somente manipulador de I / O, que pode ser chamada com uma indicação tal como para qualquer
out << std::endl out de std::basic_ostream tipo.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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Notas
Este manipulador pode ser utilizado para produzir uma linha de saída, imediatamente, por exemplo, ao exibir a saída de um processo de longa duração, o registro da atividade de vários segmentos ou registrar a atividade de um programa que pode falhar inesperadamente. Um esvaziamento explícito de std::cout também é necessária antes de uma chamada para std::system, se o processo gerado executa qualquer tela de I / O (um exemplo comum é
std::system("pause") no Windows). Na maioria dos outros habituais interativos / S cenários, std::endl é redundante quando usado com std::cout porque qualquer entrada de std::cin, saída para std::cerr, ou término do programa obriga uma chamada para std::cout.flush(). Uso de std::endl no lugar de '\n', incentivado por algumas fontes, pode degradar significativamente o desempenho saída.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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Em muitas implementações, a saída padrão é a linha-buffered, e
'\n' escrita provoca uma descarga de qualquer maneira, a menos que std::cout.sync_with_stdio(false) foi executado. Nessas situações, endl desnecessário só degrada o desempenho de saída de arquivo não, a saída padrão.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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Os exemplos de código neste follow Bjarne Stroustrup wiki em Flushing a saída padrão apenas quando necessário.
Original:
The code samples on this wiki follow Bjarne Stroustrup in flushing the standard output only where necessary.
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Quando uma linha incompleta de saída tem de ser lavada, o manipulador std::flush podem ser utilizados.
Original:
When an incomplete line of output needs to be flushed, the std::flush manipulator may be used.
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Quando todos os caracteres de saída precisa ser lavada, o manipulador std::unitbuf pode ser usado.
Original:
When every character of output needs to be flushed, the std::unitbuf manipulator may be used.
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Parâmetros
| os | - | referência ao fluxo de saída
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. |
Valor de retorno
os (referência ao fluxo após a manipulação)Original:
os (reference to the stream after manipulation)The text has been machine-translated via Google Translate.
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Exemplo
Com \ n em vez de endl, o resultado seria o mesmo, mas não pode aparecer em tempo real .
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);
}
}
Saída:
487 ms passed
974 ms passed
1470 ms passed
1965 ms passed
2455 ms passed
Veja também
controles se a saída é liberada após cada operação 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. (função) | |
libera o fluxo de saída 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. (modelo de função) | |
sincroniza com o dispositivo de armazenamento subjacente 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. (of std::basic_ostream função pública membro)
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