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std::fread

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< cpp‎ | io‎ | c

 
 
D'entrée / sortie de bibliothèque
I / O manipulateurs
C-style I / O
Tampons
Original:
Buffers
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basic_streambuf
basic_filebuf
basic_stringbuf
strstreambuf (obsolète)
Cours d'eau
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Streams
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Abstractions
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Abstractions
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ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
Fichier E / O
Original:
File I/O
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basic_ifstream
basic_ofstream
basic_fstream
Chaîne I / O
Original:
String I/O
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basic_istringstream
basic_ostringstream
basic_stringstream
Tableau I / O
Original:
Array I/O
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istrstream (obsolète)
ostrstream (obsolète)
strstream (obsolète)
Types
Original:
Types
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streamoff
streamsize
fpos
Interface catégorie d'erreur
Original:
Error category interface
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iostream_category (C++11)
io_errc (C++11)
 
C-style I / O
Fonctions
Original:
Functions
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Déposer accès
Original:
File access
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Entrée / sortie directe
Original:
Direct input/output
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fread
fwrite
Entrée non formatée / sortie
Original:
Unformatted input/output
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Mise en forme d'entrée / sortie
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Formatted input/output
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Fichier de positionnement
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File positioning
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ftell
fgetpos
fseek
fsetpos
rewind
Erreur de manipulation
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Error handling
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clearerr
feof
ferror
perror
Les opérations sur les fichiers
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Operations on files
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remove
rename
tmpfile
tmpnam
 
Defined in header <cstdio>
std::size_t fread( void* buffer, std::size_t size, std::size_t count, std::FILE* stream );
Lit jusqu'à count objets dans le tableau buffer à partir du courant d'entrée donné stream comme par appel std::fgetc size fois pour chaque objet, et mémoriser les résultats, dans l'ordre obtenu, dans les positions successives de buffer, qui est réinterprété comme un tableau d' unsigned char. L'indicateur de position de fichier pour le flux avance du nombre de caractères lus .
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.
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Si les objets ne sont pas TriviallyCopyable, le comportement est indéfini .
Original:
If the objects are not TriviallyCopyable, the behavior is undefined.
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Si une erreur se produit, la valeur résultante de l'indicateur de position du flux est
Original:
If an error occurs, the resulting value of the file position indicator for the stream is
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indéterminée. Si un élément partiel est lu, sa valeur est indéterminée
Original:
indeterminate. If a partial element is read, its value is indeterminate
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Sommaire

[modifier] Paramètres

buffer -
pointeur vers le premier objet dans le tableau doivent être lues
Original:
pointer to the first object in the array to be read
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size -
taille de chaque objet en octets
Original:
size of each object in bytes
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count -
le nombre d'objets à lire
Original:
the number of the objects to be read
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[modifier] Retourne la valeur

Nombre d'objets lus avec succès, ce qui peut être inférieure à count si une condition d'erreur ou de fin de fichier est atteinte .
Original:
Number of objects read successfully, which may be less than count if an error or end-of-file condition occurs.
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Si size ou count est égal à zéro, fread renvoie zéro et n'effectue aucune autre action .
Original:
If size or count is zero, fread returns zero and performs no other action.
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[modifier] Exemple

#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);
}

Résultat :

1 2

[modifier] Voir aussi

lit l'entrée en forme à partir stdin, un flux de fichier ou un tampon
Original:
reads formatted input from stdin, a file stream or a buffer
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(fonction) [edit]
reçoit une chaîne de caractères à partir d'un flux de fichier
Original:
gets a character string from a file stream
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(fonction) [edit]
écrit dans un fichier
Original:
writes to a file
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(fonction) [edit]
C documentation for fread