stdgetlinestdcin

std::getline and std::cin are central to reading lines in C++. The function std::getline reads characters from an input stream into a string until a delimiter is encountered, defaulting to the newline character. It is defined in the standard library and is commonly used with std::string, but there are overloads for other character types, such as std::wstring with std::wcin.

The typical form is std::getline(std::istream& is, std::string& s); a second form allows a custom delimiter: std::getline(std::istream& is, std::string& s, char delim); There are analogous overloads for wide strings when using std::wcin and std::wstring. The function reads characters from is, appends them to s, and stops when the delimiter is found or end-of-file is reached. The delimiter is extracted from the stream but not stored in s. The function returns the stream, enabling expression chaining.

Usage examples are straightforward: std::string line; std::getline(std::cin, line); reads a line from standard input into line. With a different delimiter: std::getline(std::cin, line, ';'); reads up to the first semicolon. If the end of file is reached before any characters are extracted, the stream enters an EOF state; if characters were read, they are stored in the string and the function may set eofbit.

Common pitfalls include mixing operator>> and std::getline, which can leave a newline in the buffer and cause an empty line to be read. A typical fix is to clear the input buffer first, for example using std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n') before calling getline.

Overall, std::getline provides a safe, convenient way to read whole lines from streams into strings, with flexible delimiter support and consistent behavior across char and wchar_t variants.