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std::setbuf(3) C++ Standard Libary std::setbuf(3) NAME std::setbuf - std::setbuf Synopsis Defined in header <cstdio> void setbuf( std::FILE* stream, char* buffer ); Sets the internal buffer to use for I/O operations performed on the C stream stream. If buffer is not null, equivalent to std::setvbuf(stream, buffer, _IOFBF, BUFSIZ) If buffer is null, equivalent to std::setvbuf(stream, nullptr, _IONBF, 0), which turns off buffering. Parameters stream - the file stream to set the buffer to. pointer to a buffer for the stream to use. If a null pointer is supplied, buffer - the buffering is turned off. If not null, must be able to hold at least BUFSIZ characters Return value (none) Notes If BUFSIZ is not the appropriate buffer size, std::setvbuf can be used to change it. std::setvbuf should also be used to detect errors, since std::setbuf does not indicate success or failure. This function may only be used after stream has been associated with an open file, but before any other operation (other than a failed call to std::setbuf/std::setvbuf). A common error is setting the buffer of stdin or stdout to an array whose lifetime ends before the program terminates: int main() { char buf[BUFSIZ]; std::setbuf(stdin, buf); } // lifetime of buf ends, undefined behavior Example std::setbuf may be used to disable buffering on streams that require immediate output // Run this code #include <cstdio> #include <thread> #include <chrono> int main() { using namespace std::chrono_literals; std::setbuf(stdout, nullptr); // unbuffered stdout std::putchar('a'); // appears immediately on unbuffered stream std::this_thread::sleep_for(1s); std::putchar('b'); } Output: ab See also setvbuf sets the buffer and its size for a file stream (function) http://cppreference.com 2022.07.31 std::setbuf(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Output: | See also
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