std :: string格式化如sprintf [英] std::string formatting like sprintf

问题描述

我必须格式化 std :: string 使用 sprintf 并发送到文件流。如何做到这一点？

I have to format std::string with sprintf and send it into file stream. How can I do this?

推荐答案

你不能直接做，因为你没有对底层缓冲区（直到C ++ 11;参见Dietrich Epp的注释）。你必须先在c字符串中做，然后将其复制到std :: string：

You can't do it directly, because you don't have write access to the underlying buffer (until C++11; see Dietrich Epp's comment). You'll have to do it first in a c-string, then copy it into a std::string:

  char buff[100];
  snprintf(buff, sizeof(buff), "%s", "Hello");
  std::string buffAsStdStr = buff;

但我不知道为什么你不会只使用字符串流？我假设你有具体的原因，不只是这样做：

But I'm not sure why you wouldn't just use a string stream? I'm assuming you have specific reasons to not just do this:

  std::ostringstream stringStream;
  stringStream << "Hello";
  std::string copyOfStr = stringStream.str();

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