没有这个功能.可以通过读取整行来进行计数

There is no such function. Counting can be done by reading whole lines

std::ifstream f("text.txt");
std::string line;
long i;
for (i = 0; std::getline(f, line); ++i)
    ;

关于作用域的说明，变量 i 必须在 for，如果你想在循环后访问它.

A note about scope, variable i must be outside for, if you want to access it after the loop.

您也可以逐字阅读并检查换行符

You may also read character-wise and check for linefeeds

std::ifstream f("text.txt");
char c;
long i = 0;
while (f.get(c))
    if (c == '
')
        ++i;