std::fread
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| definiert in Header <cstdio>
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| std::size_t fread( void* buffer, std::size_t size, std::size_t count, std::FILE* stream ); |
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Liest bis zu
count Gegenstände in dem Array buffer von dem gegebenen Eingabestrom stream wie durch calling std::fgetc size Zeiten für jedes Objekt, und Speicherung der Ergebnisse in der Reihenfolge erhalten wurde, in die aufeinanderfolgenden Positionen buffer, die als ein Array von interpretiert wird unsigned char. Die Datei Stellungsanzeige für den Strom wird durch die Anzahl der gelesenen Zeichen vorgeschoben .Original:
Reads up to
count objects into the array buffer from the given input stream stream as if by calling std::fgetc size times for each object, and storing the results, in the order obtained, into the successive positions of buffer, which is reinterpreted as an array of unsigned char. The file position indicator for the stream is advanced by the number of characters read.The text has been machine-translated via Google Translate.
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Wenn die Objekte nicht
TriviallyCopyable, ist das Verhalten undefiniert .Original:
If the objects are not
TriviallyCopyable, the behavior is undefined.The text has been machine-translated via Google Translate.
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Wenn ein Fehler auftritt, ist der resultierende Wert der Dateipositionszeigers für den Strom
Original:
If an error occurs, the resulting value of the file position indicator for the stream is
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unbestimmt. Wenn ein Teilelement gelesen wird, ist sein Wert unbestimmt
Original:
indeterminate. If a partial element is read, its value is indeterminate
The text has been machine-translated via Google Translate.
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Inhaltsverzeichnis |
[Bearbeiten] Parameter
| buffer | - | Zeiger auf das erste Objekt in dem Array zu lesen
Original: pointer to the first object in the array to be read The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| size | - | Größe jedes Objekts in Bytes
Original: size of each object in bytes The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| count | - | die Anzahl der Objekte zu lesen
Original: the number of the objects to be read The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
[Bearbeiten] Rückgabewert
Anzahl der Objekte erfolgreich gelesen, was weniger sein kann als
count wenn ein Fehler oder End-of-File-Bedingung auftritt . Original:
Number of objects read successfully, which may be less than
count if an error or end-of-file condition occurs. The text has been machine-translated via Google Translate.
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Wenn
size oder count Null ist, gibt fread Null und führt keine weitere Aktion .Original:
If
size or count is zero, fread returns zero and performs no other action.The text has been machine-translated via Google Translate.
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[Bearbeiten] Beispiel
#include <iostream> #include <cstdio> #include <fstream> #include <vector> int main() { // prepare file std::ofstream("test.txt") << 1 << ' ' << 2 << '\n'; std::FILE* f = std::fopen("test.txt", "r"); std::vector<char> buf(4); // char is trivally copyable std::fread(&buf[0], sizeof buf[0], buf.size(), f); for(char n : buf) std::cout << n; std::vector<std::string> buf2; // string is not trivially copyable // this would result in undefined behavior // std::fread(&buf2[0], sizeof buf2[0], buf2.size(), f); }
Output:
1 2
[Bearbeiten] Siehe auch
| liest formatierten Eingaben von stdin, eine Datei-Strom oder einen Puffer Original: reads formatted input from stdin, a file stream or a buffer The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) | |
| erhält eine Zeichenkette aus einem Datei-Stream Original: gets a character string from a file stream The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) | |
| eine Datei schreibt Original: writes to a file The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) | |
| C documentation for fread
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