std::fwrite

Header: <cstdio>

Writes up to count binary objects from the given array buffer to the output stream stream. The objects are written as if by reinterpreting each object as an array of unsigned char and calling std::fputc size times for each object to write those unsigned chars into stream, in order. The file position indicator for the stream is advanced by the number of characters written.

# Declarations

std::size_t fwrite( const void* buffer, std::size_t size, std::size_t count, std::FILE* stream );

# Parameters

# Return value

Number of objects written successfully, which may be less than count if an error occurred.

# Example

#include <array>
#include <cstdio>
#include <vector>
 
int main ()
{
    // write buffer to file
    if (std::FILE* f1 = std::fopen("file.bin", "wb"))
    {
        std::array<int, 3> v = {42, -1, 7}; // underlying storage of std::array is an array
        std::fwrite(v.data(), sizeof v[0], v.size(), f1);
        std::fclose(f1);
    }
 
    // read the same data and print it to the standard output
    if (std::FILE* f2 = std::fopen("file.bin", "rb"))
    {
        std::vector<int> rbuf(10); // underlying storage of std::vector is also an array
        std::size_t sz = std::fread(rbuf.data(), sizeof rbuf[0], rbuf.size(), f2);
        std::fclose(f2);
        for (std::size_t n = 0; n < sz; ++n)
            std::printf("%d\n", rbuf[n]);
    }
}

# See also