c++ 20有std::format，它在API方面类似于sprintf，但完全是类型安全的，适用于用户定义的类型，并使用类似python的格式字符串语法。下面是如何格式化std::string并将其写入流的方法:

std::string s = "foo";
std::cout << std::format("Look, a string: {}", s);

或者，你可以使用{fmt}库格式化字符串，并将其写入标准输出或文件流:

fmt::print("Look, a string: {}", s);

至于sprintf或这里的大多数其他答案，不幸的是，它们使用了可变参数，并且本质上是不安全的，除非您使用类似GCC的format属性，它只适用于文字格式字符串。你可以在下面的例子中看到为什么这些函数是不安全的:

std::string format_str = "%s";
string_format(format_str, format_str[0]);

其中string_format是Erik Aronesty的答案的实现。这段代码可以编译，但是当你试图运行它时，它很可能会崩溃:

$ g++ -Wall -Wextra -pedantic test.cc 
$ ./a.out 
Segmentation fault: 11

免责声明:我是{fmt}和c++ 20 std::format的作者。

以下是我的(简单的解决方案):

std::string Format(const char* lpszFormat, ...)
{
    // Warning : "vsnprintf" crashes with an access violation
    // exception if lpszFormat is not a "const char*" (for example, const string&)

    size_t  nSize     = 1024;
    char    *lpBuffer = (char*)malloc(nSize);

    va_list lpParams;

    while (true)
    {
        va_start(lpParams, lpszFormat);

        int nResult = vsnprintf(
            lpBuffer,
            nSize,
            lpszFormat,
            lpParams
        );

        va_end(lpParams);

        if ((nResult >= 0) && (nResult < (int)nSize) )
        {
            // Success

            lpBuffer[nResult] = '\0';
            std::string sResult(lpBuffer);

            free (lpBuffer);

            return sResult;
        }
        else
        {
            // Increase buffer

            nSize =
                  (nResult < 0)
                ? nSize *= 2
                : (nResult + 1)
            ;

            lpBuffer = (char *)realloc(lpBuffer, nSize);
        }
    }
}

如果你只想要一个类似printf的语法(不需要自己调用printf)，可以看看Boost Format。

到目前为止，所有的答案似乎都有一个或多个这样的问题:(1)它可能无法在vc++上工作(2)它需要额外的依赖，如boost或fmt(3)它太复杂的自定义实现，可能没有经过很好的测试。

下面的代码解决了上述所有问题。

#include <string>
#include <cstdarg>
#include <memory>

std::string stringf(const char* format, ...)
{
    va_list args;
    va_start(args, format);
    #ifndef _MSC_VER

        //GCC generates warning for valid use of snprintf to get
        //size of result string. We suppress warning with below macro.
        #ifdef __GNUC__
        #pragma GCC diagnostic push
        #pragma GCC diagnostic ignored "-Wformat-nonliteral"
        #endif

        size_t size = std::snprintf(nullptr, 0, format, args) + 1; // Extra space for '\0'

        #ifdef __GNUC__
        # pragma GCC diagnostic pop
        #endif

        std::unique_ptr<char[]> buf(new char[ size ] ); 
        std::vsnprintf(buf.get(), size, format, args);
        return std::string(buf.get(), buf.get() + size - 1 ); // We don't want the '\0' inside
    #else
        int size = _vscprintf(format, args);
        std::string result(++size, 0);
        vsnprintf_s((char*)result.data(), size, _TRUNCATE, format, args);
        return result;
    #endif
    va_end(args);
}    

int main() {
    float f = 3.f;
    int i = 5;
    std::string s = "hello!";
    auto rs = stringf("i=%d, f=%f, s=%s", i, f, s.c_str());
    printf("%s", rs.c_str());
    return 0;
}

注:

Separate VC++ code branch is necessary because VC++ has decided to deprecate snprintf which will generate compiler warnings for other highly voted answers above. As I always run in "warnings as errors" mode, its no go for me. The function accepts char * instead of std::string. This because most of the time this function would be called with literal string which is indeed char *, not std::string. In case you do have std::string as format parameter, then just call .c_str(). Name of the function is stringf instead of things like string_format to keepup with printf, scanf etc. It doesn't address safety issue (i.e. bad parameters can potentially cause seg fault instead of exception). If you need this then you are better off with boost or fmt libraries. My preference here would be fmt because it is just one header and source file to drop in the project while having less weird formatting syntax than boost. However both are non-compatible with printf format strings so below is still useful in that case. The stringf code passes through GCC strict mode compilation. This requires extra #pragma macros to suppress false positives in GCC warnings.

以上代码已在，

GCC 4.9.2 11 / c++ / C + + 14 vc++编译器19.0 铿锵声3.7.0

这是可以尝试的。简单。虽然没有使用字符串类的细微差别。

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

#include <string>
#include <exception>
using namespace std;

//---------------------------------------------------------------------

class StringFormatter
{
public:
    static string format(const char *format, ...);
};

string StringFormatter::format(const char *format, ...)
{
    va_list  argptr;

    va_start(argptr, format);

        char   *ptr;
        size_t  size;
        FILE   *fp_mem = open_memstream(&ptr, &size);
        assert(fp_mem);

        vfprintf (fp_mem, format, argptr);
        fclose (fp_mem);

    va_end(argptr);

    string ret = ptr;
    free(ptr);

    return ret;
}

//---------------------------------------------------------------------

int main(void)
{
    string temp = StringFormatter::format("my age is %d", 100);
    printf("%s\n", temp.c_str());

    return 0;
}

我用vsnprintf写了我自己的，所以它返回字符串，而不是必须创建我自己的缓冲区。

#include <string>
#include <cstdarg>

//missing string printf
//this is safe and convenient but not exactly efficient
inline std::string format(const char* fmt, ...){
    int size = 512;
    char* buffer = 0;
    buffer = new char[size];
    va_list vl;
    va_start(vl, fmt);
    int nsize = vsnprintf(buffer, size, fmt, vl);
    if(size<=nsize){ //fail delete buffer and try again
        delete[] buffer;
        buffer = 0;
        buffer = new char[nsize+1]; //+1 for /0
        nsize = vsnprintf(buffer, size, fmt, vl);
    }
    std::string ret(buffer);
    va_end(vl);
    delete[] buffer;
    return ret;
}

所以你可以用它

std::string mystr = format("%s %d %10.5f", "omg", 1, 10.5);