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The C++ std::istream::read() function is used to read a specified number of characters from an input stream into a buffer. It is commonly employed for binary input operations. This function takes two arguments: a pointer to the buffer where data will be stored and the number of characters to read.

Syntax

Following is the syntax for std::istream::read() function.

istream& read (char* s, streamsize n);

Parameters

• n − It indicates the number of characters to extract.
• s − It indicates the pointer to an array where the extracted characters are stored.

Return Value

This function returns the basic_istream object (*this).

Exceptions

If an exception is thrown, the object is in a valid state.

Data races

Modifies the elements in the array pointed by s and the stream object.

Example

In the following example, where we are going to consider the basic usage of read() function.

#include <iostream>
#include <sstream>
int main()
{
    std::istringstream a("Hi, Namaste");
    char b[6];
    a.read(b, 2);
    b[2] = '\0';
    std::cout << "Result : " << b << std::endl;
    return 0;
}

Output

Following is the output of the above code −

Result : Hi

Example

Consider the following example, where we are going to read the 4-byte integer from the integer stream.

#include <iostream>
#include <sstream>
int main()
{
    std::istringstream x("\x11\x10\x00\01");
    int a;
    x.read(reinterpret_cast<char*>(&a), sizeof(a));
    std::cout << "Result : " << a << std::endl;
    return 0;
}

Output

If we run the above code it will generate the following output −

Result : 4113

istream.htm