template<typename... Args>
std::string string_format(const char* fmt, Args... args)
{
    size_t size = snprintf(nullptr, 0, fmt, args...);
    std::string buf;
    buf.reserve(size + 1);
    buf.resize(size);
    snprintf(&buf[0], size + 1, fmt, args...);
    return buf;
}

使用C99 snprintf和c++ 11

我通常用这个:

std::string myformat(const char *const fmt, ...)
{
        char *buffer = NULL;
        va_list ap;

        va_start(ap, fmt);
        (void)vasprintf(&buffer, fmt, ap);
        va_end(ap);

        std::string result = buffer;
        free(buffer);

        return result;
}

缺点:并非所有系统都支持vasprint

我知道这个问题已经被回答过很多次了，但下面这个更简洁:

std::string format(const std::string fmt_str, ...)
{
    va_list ap;
    char *fp = NULL;
    va_start(ap, fmt_str);
    vasprintf(&fp, fmt_str.c_str(), ap);
    va_end(ap);
    std::unique_ptr<char[]> formatted(fp);
    return std::string(formatted.get());
}

例子:

#include <iostream>
#include <random>

int main()
{
    std::random_device r;
    std::cout << format("Hello %d!\n", r());
}

参见http://rextester.com/NJB14150

可以使用iomanip头文件格式化cout中的c++输出。 在使用类似的任何helper函数之前，请确保包含iomanip头文件 Setprecision, setfill等等。

下面是我过去用来在向量中打印平均等待时间的代码片段，这是我“累积”的。

#include<iomanip>
#include<iostream>
#include<vector>
#include<numeric>

...

cout<< "Average waiting times for tasks is " << setprecision(4) << accumulate(all(waitingTimes), 0)/double(waitingTimes.size()) ;
cout << " and " << Q.size() << " tasks remaining" << endl;

下面是如何格式化c++流的简要描述。 http://www.cprogramming.com/tutorial/iomanip.html

这是我用来在我的程序中这样做的代码…这没什么特别的，但很管用……注意，您必须根据需要调整您的尺寸。我的MAX_BUFFER是1024。

std::string Format ( const char *fmt, ... )
{
    char textString[MAX_BUFFER*5] = {'\0'};

    // -- Empty the buffer properly to ensure no leaks.
    memset(textString, '\0', sizeof(textString));

    va_list args;
    va_start ( args, fmt );
    vsnprintf ( textString, MAX_BUFFER*5, fmt, args );
    va_end ( args );
    std::string retStr = textString;
    return retStr;
}

从Dacav和pixelpoint的答案中获得灵感。我玩了一下，得到了这个:

#include <cstdarg>
#include <cstdio>
#include <string>

std::string format(const char* fmt, ...)
{
    va_list vl;

    va_start(vl, fmt);
    int size = vsnprintf(0, 0, fmt, vl) + sizeof('\0');
    va_end(vl);

    char buffer[size];

    va_start(vl, fmt);
    size = vsnprintf(buffer, size, fmt, vl);
    va_end(vl);

    return std::string(buffer, size);
}

通过合理的编程实践，我相信代码应该足够了，但是我仍然对更安全的替代方案持开放态度，这些替代方案仍然足够简单，不需要c++ 11。

下面是另一个版本，它使用初始缓冲区来防止在初始缓冲区已经足够多时再次调用vsnprintf()。

std::string format(const char* fmt, ...)
{

    va_list vl;
    int size;

    enum { INITIAL_BUFFER_SIZE = 512 };

    {
        char buffer[INITIAL_BUFFER_SIZE];

        va_start(vl, fmt);
        size = vsnprintf(buffer, INITIAL_BUFFER_SIZE, fmt, vl);
        va_end(vl);

        if (size < INITIAL_BUFFER_SIZE)
            return std::string(buffer, size);
    }

    size += sizeof('\0');

    char buffer[size];

    va_start(vl, fmt);
    size = vsnprintf(buffer, size, fmt, vl);
    va_end(vl);

    return std::string(buffer, size);
}

(事实证明，这个版本与Piti Ongmongkolkul的答案相似，只是它没有使用new和delete[]，并且在创建std::string时指定了大小。

The idea here of not using new and delete[] is to imply usage of the stack over the heap since it doesn't need to call allocation and deallocation functions, however if not properly used, it could be dangerous to buffer overflows in some (perhaps old, or perhaps just vulnerable) systems. If this is a concern, I highly suggest using new and delete[] instead. Note that the only concern here is about the allocations as vsnprintf() is already called with limits, so specifying a limit based on the size allocated on the second buffer would also prevent those.)