如何将std :: string转换为C样式的字符串 [英] How to convert an std::string to C-style string
问题描述
我正在用C ++编程。
I am programming in C++.
作为这个问题的基本知识，我似乎无法在任何地方找到答案。所以这是问题所在：
As basic as this question is I cannot seem to find an answer for it anywhere. So here is the problem:
我想创建一个C风格的字符串，但是我想将一个整数变量i放入字符串中。很自然地，我使用了一个流：
I want to create a C-style string however I want to put an integer variable i into the string. So naturally, I used a stream:
stringstream foo;
foo
<< "blah blah blah blah... i = "
<< i
<< " blah blah... ";
但是，我需要以某种方式获取C风格的字符串以传递给函数（结果为foo .str（）返回std :: string）。所以从技术上讲这是一个三部分的问题-
However, I need to somehow get a C-style string to pass to a function (turns out foo.str() returns an std::string). So this is technically a three part question --
1）如何将std :: string转换为C风格的字符串？
1) How do I convert std::string to a C-style string?
2）是否可以从字符串流中获取C风格的字符串？
2) Is there a way to get a C-style string from a stringstream?
3）是否可以使用C-直接样式化字符串（不使用stringstreams）以构造其中带有整数变量的字符串？
3) Is there a way to use a C-style string directly (without using stringstreams) to construct a string with an integer variable in it?
推荐答案
1）如何将std :: string转换为C样式的字符串？
1) How do I convert std::string to a C-style string?
只需调用 string .c_str（）以获得 char const * 。如果您需要 mutable _C-style_字符串，请进行复制。只要您不调用 string 的任何非常量函数，返回的 C字符串就有效。
Simply call string.c_str() to get a char const*. If you need a mutable _C-style_ string then make a copy. The returned C string will be valid as long as you don't call any non-const function of string.
2）有没有办法从字符串流中获取C风格的字符串？
2) Is there a way to get a C-style string from a stringstream?
这里只是 strstream.str（）。c_str（）。返回的 C字符串仅在包含它的表达式的末尾才有效，这意味着将其用作函数参数是有效的，但不能存储在变量中以备后用。 / p>
There is, simply strstream.str().c_str(). The returned C string will be valid only until the end of the expression that contains it, that means that is valid to use it as a function argument but not to be stored in a variable for later access.
3）是否有一种方法可以直接使用C样式的字符串（不使用stringstreams）来构造其中带有整数变量的字符串？
3) Is there a way to use a C-style string directly (without using stringstreams) to construct a string with an integer variable in it?
有 C方式，使用 sprintf 等。
这篇关于如何将std :: string转换为C样式的字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
