blocks|key|1103046|text|您不能直接这样做，因为您没有对底层缓冲区的写访问权限(直到C%2B%2B11为止；请参阅Dietrich+Epp的comment)。您必须首先在c-string中执行此操作，然后将其复制到std：：string中：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1103047|++char+buff[100];
++snprintf(buff,+sizeof(buff),+"%25s",+"Hello");
++std::string+buffAsStdStr+=+buff;|code-block|syntax|javascript|1103048|但我不确定你为什么不直接使用字符串流？我假设你有特定的理由不这么做：|1103049|++std::ostringstream+stringStream;
++stringStream+<<+"Hello";
++std::string+copyOfStr+=+stringStream.str();|1103050|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/2342162/stdstring-formatting-like-sprintf#comment61134428_2342176^0|1H|7|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

You can't do it directly, because you don't have write access to the underlying buffer (until C++11; see Dietrich Epp's <a href="https://stackoverflow.com/questions/2342162/stdstring-formatting-like-sprintf#comment61134428_2342176">comment</a>). You'll have to do it first in a c-string, then copy it into a std::string:

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

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:

<pre><code> std::ostringstream stringStream;
 stringStream &lt;&lt; "Hello";
 std::string copyOfStr = stringStream.str();
</code></pre>

blocks|key|1318055|text|string没有您需要的东西，但std::stringstream有。使用字符串流创建字符串，然后提取字符串。Here是一个关于你可以做的事情的综合列表。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1318056|cout.setprecision(10);+//stringstream+is+a+stream+like+cout|code-block|syntax|javascript|1318057|在打印双精度或浮点数时，将为您提供10位小数精度。|1318058|entityMap|0|LINK|mutability|MUTABLE|url|http://stdcxx.apache.org/doc/stdlibug/28-3.html^0|1J|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

string doesn't have what you need, but std::stringstream does. Use a stringstream to create the string and then extract the string. <a href="http://stdcxx.apache.org/doc/stdlibug/28-3.html" rel="nofollow noreferrer">Here</a> is a comprehensive list on the things you can do. For example:

<pre><code>cout.setprecision(10); //stringstream is a stream like cout
</code></pre>

will give you 10 decimal places of precision when printing a double or float.

blocks|key|1318138|text|如果您只需要一种类似printf的语法(不需要自己调用printf)，那么可以看看Boost+Format。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1318139|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_42_0/libs/format/index.html^0|15|C|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

If you only want a printf-like syntax (without calling printf yourself), have a look at <a href="http://www.boost.org/doc/libs/1_42_0/libs/format/index.html" rel="noreferrer">Boost Format</a>.

blocks|key|1318213|text|在内部使用vsnprintf()的C%2B%2B11解决方案：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1318214|#include+<stdarg.h>++//+For+va_start,+etc.

std::string+string_format(const+std::string+fmt,+...)+{
++++int+size+=+((int)fmt.size())+*+2+%2B+50;+++//+Use+a+rubric+appropriate+for+your+code
++++std::string+str;
++++va_list+ap;
++++while+(1)+{+++++//+Maximum+two+passes+on+a+POSIX+system...
++++++++str.resize(size);
++++++++va_start(ap,+fmt);
++++++++int+n+=+vsnprintf((char+*)str.data(),+size,+fmt.c_str(),+ap);
++++++++va_end(ap);
++++++++if+(n+>+-1+&&+n+<+size)+{++//+Everything+worked
++++++++++++str.resize(n);
++++++++++++return+str;
++++++++}
++++++++if+(n+>+-1)++//+Needed+size+returned
++++++++++++size+=+n+%2B+1;+++//+For+null+char
++++++++else
++++++++++++size+*=+2;++++++//+Guess+at+a+larger+size+(OS+specific)
++++}
++++return+str;
}|code-block|syntax|javascript|1318215|一种更安全、更有效的方法(我对它进行了测试，它更快)：|1318216|#include+<stdarg.h>++//+For+va_start,+etc.
#include+<memory>++++//+For+std::unique_ptr

std::string+string_format(const+std::string+fmt_str,+...)+{
++++int+final_n,+n+=+((int)fmt_str.size())+*+2;+/*+Reserve+two+times+as+much+as+the+length+of+the+fmt_str+*/
++++std::unique_ptr<char[]>+formatted;
++++va_list+ap;
++++while(1)+{
++++++++formatted.reset(new+char[n]);+/*+Wrap+the+plain+char+array+into+the+unique_ptr+*/
++++++++strcpy(&formatted[0],+fmt_str.c_str());
++++++++va_start(ap,+fmt_str);
++++++++final_n+=+vsnprintf(&formatted[0],+n,+fmt_str.c_str(),+ap);
++++++++va_end(ap);
++++++++if+(final_n+<+0+%7C%7C+final_n+>=+n)
++++++++++++n+%2B=+abs(final_n+-+n+%2B+1);
++++++++else
++++++++++++break;
++++}
++++return+std::string(formatted.get());
}|1318217|为了符合va_start的要求，通过值传递fmt_str。|1318218|注意：“更安全”和“更快”版本在某些系统上不起作用。因此，这两种方法仍在列表中。此外，“更快”完全取决于预分配步骤是否正确，否则strcpy会使其变慢。|1318219|entityMap^0|5|B|0|0|0|0|4|8|L|7|0|1S|6|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|S|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|T|$]]

C++11 solution that uses <code>vsnprintf()</code> internally:

<pre><code>#include &lt;stdarg.h&gt; // For va_start, etc.

std::string string_format(const std::string fmt, ...) {
 int size = ((int)fmt.size()) * 2 + 50; // Use a rubric appropriate for your code
 std::string str;
 va_list ap;
 while (1) { // Maximum two passes on a POSIX system...
 str.resize(size);
 va_start(ap, fmt);
 int n = vsnprintf((char *)str.data(), size, fmt.c_str(), ap);
 va_end(ap);
 if (n &gt; -1 &amp;&amp; n &lt; size) { // Everything worked
 str.resize(n);
 return str;
 }
 if (n &gt; -1) // Needed size returned
 size = n + 1; // For null char
 else
 size *= 2; // Guess at a larger size (OS specific)
 }
 return str;
}
</code></pre>

A safer and more efficient (I tested it, and it is faster) approach:

<pre><code>#include &lt;stdarg.h&gt; // For va_start, etc.
#include &lt;memory&gt; // For std::unique_ptr

std::string string_format(const std::string fmt_str, ...) {
 int final_n, n = ((int)fmt_str.size()) * 2; /* Reserve two times as much as the length of the fmt_str */
 std::unique_ptr&lt;char[]&gt; formatted;
 va_list ap;
 while(1) {
 formatted.reset(new char[n]); /* Wrap the plain char array into the unique_ptr */
 strcpy(&amp;formatted[0], fmt_str.c_str());
 va_start(ap, fmt_str);
 final_n = vsnprintf(&amp;formatted[0], n, fmt_str.c_str(), ap);
 va_end(ap);
 if (final_n &lt; 0 || final_n &gt;= n)
 n += abs(final_n - n + 1);
 else
 break;
 }
 return std::string(formatted.get());
}
</code></pre>

The <code>fmt_str</code> is passed by value to conform with the requirements of <code>va_start</code>.

NOTE: The "safer" and "faster" version doesn't work on some systems. Hence both are still listed. Also, "faster" depends entirely on the preallocation step being correct, otherwise the <code>strcpy</code> renders it slower.

blocks|key|1103322|text|这是我在程序中用来做这件事的代码...这不是什么花哨的东西，但它确实有效..。注意，您必须根据需要调整您的尺寸。我的MAX_BUFFER是1024。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1103323|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;
}|code-block|syntax|javascript|1103324|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This is the code I use to do this in my program... It's nothing fancy, but it does the trick... Note, you will have to adjust your size as applicable. MAX_BUFFER for me is 1024.

<pre><code>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;
}
</code></pre>

blocks|key|1318317|text|我使用vsnprintf编写了自己的代码，这样它就可以返回字符串，而不必创建自己的缓冲区。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318318|#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%2B1];+//%2B1+for+/0
++++++++nsize+=+vsnprintf(buffer,+size,+fmt,+vl);
++++}
++++std::string+ret(buffer);
++++va_end(vl);
++++delete[]+buffer;
++++return+ret;
}|code-block|syntax|javascript|1318319|所以你可以像这样使用它|1318320|std::string+mystr+=+format("%25s+%25d+%2510.5f",+"omg",+1,+10.5);|1318321|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I wrote my own using vsnprintf so it returns string instead of having to create my own buffer.

<pre><code>#include &lt;string&gt;
#include &lt;cstdarg&gt;

//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&lt;=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;
}
</code></pre>

So you can use it like

<pre><code>std::string mystr = format("%s %d %10.5f", "omg", 1, 10.5);
</code></pre>

blocks|key|1318330|text|你可以试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318331|string+str;
str.resize(+_MAX_PATH+);

sprintf(+&str[0],+"%25s+%25s",+"hello",+"world"+);
//+optionals
//+sprintf_s(+&str[0],+str.length(),+"%25s+%25s",+"hello",+"world"+);+//+Microsoft
//+#include+<stdio.h>
//+snprintf(+&str[0],+str.length(),+"%25s+%25s",+"hello",+"world"+);+//+c%2B%2B11

str.resize(+strlen(+str.data()+)+%2B+1+);|code-block|syntax|javascript|1318332|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You could try this:

<pre><code>string str;
str.resize( _MAX_PATH );

sprintf( &amp;str[0], "%s %s", "hello", "world" );
// optionals
// sprintf_s( &amp;str[0], str.length(), "%s %s", "hello", "world" ); // Microsoft
// #include &lt;stdio.h&gt;
// snprintf( &amp;str[0], str.length(), "%s %s", "hello", "world" ); // c++11

str.resize( strlen( str.data() ) + 1 );
</code></pre>

blocks|key|1103430|text|根据埃里克·阿隆斯蒂提供的答案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1103431|std::string+string_format(const+std::string+&fmt,+...)+{
++++std::vector<char>+str(100,'\0');
++++va_list+ap;
++++while+(1)+{
++++++++va_start(ap,+fmt);
++++++++auto+n+=+vsnprintf(str.data(),+str.size(),+fmt.c_str(),+ap);
++++++++va_end(ap);
++++++++if+((n+>+-1)+&&+(size_t(n)+<+str.size()))+{
++++++++++++return+str.data();
++++++++}
++++++++if+(n+>+-1)
++++++++++++str.resize(+n+%2B+1+);
++++++++else
++++++++++++str.resize(+str.size()+*+2);
++++}
++++return+str.data();
}|code-block|syntax|javascript|1103432|这就避免了从原始答案中的.c_str()结果中丢弃const的需要。|offset|length|style|CODE|1103433|entityMap^0|0|0|C|8|P|5|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

Based on the answer provided by Erik Aronesty:

<pre><code>std::string string_format(const std::string &amp;fmt, ...) {
 std::vector&lt;char&gt; str(100,'\0');
 va_list ap;
 while (1) {
 va_start(ap, fmt);
 auto n = vsnprintf(str.data(), str.size(), fmt.c_str(), ap);
 va_end(ap);
 if ((n &gt; -1) &amp;&amp; (size_t(n) &lt; str.size())) {
 return str.data();
 }
 if (n &gt; -1)
 str.resize( n + 1 );
 else
 str.resize( str.size() * 2);
 }
 return str.data();
}
</code></pre>

This avoids the need to cast away <code>const</code> from the result of <code>.c_str()</code> which was in the original answer.

blocks|key|1103455|text|下面是我的(简单的解决方案)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1103456|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+%2B+1)
++++++++++++;

++++++++++++lpBuffer+=+(char+*)realloc(lpBuffer,+nSize);
++++++++}
++++}
}|code-block|syntax|javascript|1103457|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here my (simple solution):

<pre><code>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&amp;)

 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 &gt;= 0) &amp;&amp; (nResult &lt; (int)nSize) )
 {
 // Success

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

 free (lpBuffer);

 return sResult;
 }
 else
 {
 // Increase buffer

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

 lpBuffer = (char *)realloc(lpBuffer, nSize);
 }
 }
}
</code></pre>

blocks|key|1103515|text|我喜欢的一个解决方案是，在使缓冲区足够大之后，使用sprintf直接将其放入std::string+buffer中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1103516|#include+<string>
#include+<iostream>

using+namespace+std;

string+l_output;
l_output.resize(100);

for+(int+i+=+0;+i+<+1000;+%2B%2Bi)
{+++++++
++++memset+(&l_output[0],+0,+100);
++++sprintf+(&l_output[0],+"\r%25i\0",+i);

++++cout+<<+l_output;
++++cout.flush();
}|code-block|syntax|javascript|1103517|因此，创建std::string，调整它的大小，直接访问它的缓冲区...|1103518|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

One solution I've favoured is to do this with sprintf directly into the std::string buffer, after making said buffer big enough:

<pre><code>#include &lt;string&gt;
#include &lt;iostream&gt;

using namespace std;

string l_output;
l_output.resize(100);

for (int i = 0; i &lt; 1000; ++i)
{ 
 memset (&amp;l_output[0], 0, 100);
 sprintf (&amp;l_output[0], "\r%i\0", i);

 cout &lt;&lt; l_output;
 cout.flush();
}
</code></pre>

So, create the std::string, resize it, access its buffer directly...

blocks|key|1103582|text|这就是谷歌是如何做到的：StringPrintf+(BSD+License)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1103583|而facebook以一种非常类似的方式做到了：StringPrintf+(Apache+License)。|1103584|它们也都提供了一个方便的StringAppendF。|1103585|entityMap|0|LINK|mutability|MUTABLE|url|http://src.chromium.org/viewvc/chrome/trunk/src/base/strings/stringprintf.cc|1|https://github.com/facebook/folly/blob/master/folly/String.cpp^0|C|C|C|C|0|0|N|C|N|C|1|0|C|D|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]]|D|@$9|W|A|X|1|Y]]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@$9|12|A|13|1|14]]|E|$]]|$1|H|3|I|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]|R|$5|M|N|O|E|$P|S]]]]

This is how google does it: <a href="http://src.chromium.org/viewvc/chrome/trunk/src/base/strings/stringprintf.cc" rel="noreferrer"><code>StringPrintf</code></a> (BSD License) 
and facebook does it in a quite similar fashion: <a href="https://github.com/facebook/folly/blob/master/folly/String.cpp" rel="noreferrer"><code>StringPrintf</code></a> (Apache License) 
Both provide with a convenient <code>StringAppendF</code> too.

blocks|key|1103619|text|对于Visual+C|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1103620|std::wstring+stringFormat(const+wchar_t*+fmt,+...)
{
++++if+(!fmt)+{
++++++++return+L"";
++++}

++++std::vector<wchar_t>+buff;
++++size_t+size+=+wcslen(fmt)+*+2;
++++buff.resize(size);
++++va_list+ap;
++++va_start(ap,+fmt);
++++while+(true)+{
++++++++int+ret+=+_vsnwprintf_s(buff.data(),+size,+_TRUNCATE,+fmt,+ap);
++++++++if+(ret+!=+-1)
++++++++++++break;
++++++++else+{
++++++++++++size+*=+2;
++++++++++++buff.resize(size);
++++++++}
++++}
++++va_end(ap);
++++return+std::wstring(buff.data());
}|code-block|syntax|javascript|1103621|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Visual_C%252B%252B#32-bit_versions^0|2|8|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

For <a href="http://en.wikipedia.org/wiki/Visual_C%2B%2B#32-bit_versions" rel="nofollow">Visual C</a>:

<pre><code>std::wstring stringFormat(const wchar_t* fmt, ...)
{
 if (!fmt) {
 return L"";
 }

 std::vector&lt;wchar_t&gt; buff;
 size_t size = wcslen(fmt) * 2;
 buff.resize(size);
 va_list ap;
 va_start(ap, fmt);
 while (true) {
 int ret = _vsnwprintf_s(buff.data(), size, _TRUNCATE, fmt, ap);
 if (ret != -1)
 break;
 else {
 size *= 2;
 buff.resize(size);
 }
 }
 va_end(ap);
 return std::wstring(buff.data());
}
</code></pre>

blocks|key|1318584|text|inline+void+format(string&+a_string,+const+char*+fmt,+...)
{
++++va_list+vl;
++++va_start(vl,+fmt);
++++int+size+=+_vscprintf(+fmt,+vl+);
++++a_string.resize(+%2B%2Bsize+);
++++vsnprintf_s((char*)a_string.data(),+size,+_TRUNCATE,+fmt,+vl);
++++va_end(vl);
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1318585|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>inline void format(string&amp; a_string, const char* fmt, ...)
{
 va_list vl;
 va_start(vl, fmt);
 int size = _vscprintf( fmt, vl );
 a_string.resize( ++size );
 vsnprintf_s((char*)a_string.data(), size, _TRUNCATE, fmt, vl);
 va_end(vl);
}
</code></pre>

blocks|key|1318649|text|您可以使用iomanip头文件在cout中格式化C%2B%2B输出。在使用任何帮助函数之前，请确保包含iomanip头文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318650|这是我过去用来打印向量中平均等待时间的代码片段，我已经“累积”了。|1318651|#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;|code-block|syntax|javascript|1318652|下面是我们如何格式化C%2B%2B流的简要描述。http://www.cprogramming.com/tutorial/iomanip.html|offset|length|1318653|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cprogramming.com/tutorial/iomanip.html^0|0|0|0|K|1D|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@$K|Y|L|Z|1|10]]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

You can format C++ output in cout using iomanip header file.
Make sure that you include iomanip header file before you use any of the helper functions like
setprecision, setfill etc.

Here is a code snippet I have used in the past to print the average waiting time in the vector, which I have "accumulated".

<pre><code>#include&lt;iomanip&gt;
#include&lt;iostream&gt;
#include&lt;vector&gt;
#include&lt;numeric&gt;

...

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

Here is a brief description of how we can format C++ streams.
<a href="http://www.cprogramming.com/tutorial/iomanip.html" rel="nofollow">http://www.cprogramming.com/tutorial/iomanip.html</a>

blocks|key|1103736|text|如果缓冲区不够大，无法打印字符串，则可能会出现问题。必须先确定格式化字符串的长度，然后才能在其中打印格式化消息。我做了自己的助手(在Windows和Linux+GCC上测试过)，你可以试着使用它。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1103737|String.cpp：http://pastebin.com/DnfvzyKP|1103738|H：http://pastebin.com/7U6iCUMa|1103739|String.cpp：|1103740|#include+<cstdio>
#include+<cstdarg>
#include+<cstring>
#include+<string>

using+::std::string;

#pragma+warning(disable+:+4996)

#ifndef+va_copy
#ifdef+_MSC_VER
#define+va_copy(dst,+src)+dst=src
#elif+!(__cplusplus+>=+201103L+%7C%7C+defined(__GXX_EXPERIMENTAL_CXX0X__))
#define+va_copy(dst,+src)+memcpy((void*)dst,+(void*)src,+sizeof(*src))
#endif
#endif

///
///+\breif+Format+message
///+\param+dst+String+to+store+formatted+message
///+\param+format+Format+of+message
///+\param+ap+Variable+argument+list
///
void+toString(string+&dst,+const+char+*format,+va_list+ap)+throw()+{
++int+length;
++va_list+apStrLen;
++va_copy(apStrLen,+ap);
++length+=+vsnprintf(NULL,+0,+format,+apStrLen);
++va_end(apStrLen);
++if+(length+>+0)+{
++++dst.resize(length);
++++vsnprintf((char+*)dst.data(),+dst.size()+%2B+1,+format,+ap);
++}+else+{
++++dst+=+"Format+error!+format:+";
++++dst.append(format);
++}
}

///
///+\breif+Format+message
///+\param+dst+String+to+store+formatted+message
///+\param+format+Format+of+message
///+\param+...+Variable+argument+list
///
void+toString(string+&dst,+const+char+*format,+...)+throw()+{
++va_list+ap;
++va_start(ap,+format);
++toString(dst,+format,+ap);
++va_end(ap);
}

///
///+\breif+Format+message
///+\param+format+Format+of+message
///+\param+...+Variable+argument+list
///
string+toString(const+char+*format,+...)+throw()+{
++string+dst;
++va_list+ap;
++va_start(ap,+format);
++toString(dst,+format,+ap);
++va_end(ap);
++return+dst;
}

///
///+\breif+Format+message
///+\param+format+Format+of+message
///+\param+ap+Variable+argument+list
///
string+toString(const+char+*format,+va_list+ap)+throw()+{
++string+dst;
++toString(dst,+format,+ap);
++return+dst;
}


int+main()+{
++int+a+=+32;
++const+char+*+str+=+"This+works!";

++string+test(toString("\nSome+testing:+a+=+%25d,+%25s\n",+a,+str));
++printf(test.c_str());

++a+=+0x7fffffff;
++test+=+toString("\nMore+testing:+a+=+%25d,+%25s\n",+a,+"This+works+too..");
++printf(test.c_str());

++a+=+0x80000000;
++toString(test,+"\nMore+testing:+a+=+%25d,+%25s\n",+a,+"This+way+is+cheaper");
++printf(test.c_str());

++return+0;
}|code-block|syntax|javascript|1103741|String.h：|1103742|#pragma+once
#include+<cstdarg>
#include+<string>

using+::std::string;

///
///+\breif+Format+message
///+\param+dst+String+to+store+formatted+message
///+\param+format+Format+of+message
///+\param+ap+Variable+argument+list
///
void+toString(string+&dst,+const+char+*format,+va_list+ap)+throw();
///
///+\breif+Format+message
///+\param+dst+String+to+store+formatted+message
///+\param+format+Format+of+message
///+\param+...+Variable+argument+list
///
void+toString(string+&dst,+const+char+*format,+...)+throw();
///
///+\breif+Format+message
///+\param+format+Format+of+message
///+\param+...+Variable+argument+list
///
string+toString(const+char+*format,+...)+throw();

///
///+\breif+Format+message
///+\param+format+Format+of+message
///+\param+ap+Variable+argument+list
///
string+toString(const+char+*format,+va_list+ap)+throw();|1103743|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/GNU_Compiler_Collection|1|http://pastebin.com/DnfvzyKP|2|http://pastebin.com/7U6iCUMa^0|28|3|0|0|B|S|1|0|2|S|2|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@$A|15|B|16|1|17]]|C|$]]|$1|D|3|E|5|6|7|18|8|@]|9|@$A|19|B|1A|1|1B]]|C|$]]|$1|F|3|G|5|6|7|1C|8|@]|9|@$A|1D|B|1E|1|1F]]|C|$]]|$1|H|3|I|5|6|7|1G|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|1H|8|@]|9|@]|C|$M|N]]|$1|O|3|P|5|6|7|1I|8|@]|9|@]|C|$]]|$1|Q|3|R|5|L|7|1J|8|@]|9|@]|C|$M|N]]|$1|S|3|-4|5|6|7|1K|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]|10|$5|V|W|X|C|$Y|11]]|12|$5|V|W|X|C|$Y|13]]]]

There can be problems, if the buffer is not large enough to print the string. You must determine the length of the formatted string before printing a formatted message in there.
I make own helper to this (tested on Windows and Linux <a href="http://en.wikipedia.org/wiki/GNU_Compiler_Collection" rel="nofollow">GCC</a>), and you can try use it.

String.cpp: <a href="http://pastebin.com/DnfvzyKP" rel="nofollow">http://pastebin.com/DnfvzyKP</a> 
String.h: <a href="http://pastebin.com/7U6iCUMa" rel="nofollow">http://pastebin.com/7U6iCUMa</a>

String.cpp:

<pre><code>#include &lt;cstdio&gt;
#include &lt;cstdarg&gt;
#include &lt;cstring&gt;
#include &lt;string&gt;

using ::std::string;

#pragma warning(disable : 4996)

#ifndef va_copy
#ifdef _MSC_VER
#define va_copy(dst, src) dst=src
#elif !(__cplusplus &gt;= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__))
#define va_copy(dst, src) memcpy((void*)dst, (void*)src, sizeof(*src))
#endif
#endif

///
/// \breif Format message
/// \param dst String to store formatted message
/// \param format Format of message
/// \param ap Variable argument list
///
void toString(string &amp;dst, const char *format, va_list ap) throw() {
 int length;
 va_list apStrLen;
 va_copy(apStrLen, ap);
 length = vsnprintf(NULL, 0, format, apStrLen);
 va_end(apStrLen);
 if (length &gt; 0) {
 dst.resize(length);
 vsnprintf((char *)dst.data(), dst.size() + 1, format, ap);
 } else {
 dst = "Format error! format: ";
 dst.append(format);
 }
}

///
/// \breif Format message
/// \param dst String to store formatted message
/// \param format Format of message
/// \param ... Variable argument list
///
void toString(string &amp;dst, const char *format, ...) throw() {
 va_list ap;
 va_start(ap, format);
 toString(dst, format, ap);
 va_end(ap);
}

///
/// \breif Format message
/// \param format Format of message
/// \param ... Variable argument list
///
string toString(const char *format, ...) throw() {
 string dst;
 va_list ap;
 va_start(ap, format);
 toString(dst, format, ap);
 va_end(ap);
 return dst;
}

///
/// \breif Format message
/// \param format Format of message
/// \param ap Variable argument list
///
string toString(const char *format, va_list ap) throw() {
 string dst;
 toString(dst, format, ap);
 return dst;
}


int main() {
 int a = 32;
 const char * str = "This works!";

 string test(toString("\nSome testing: a = %d, %s\n", a, str));
 printf(test.c_str());

 a = 0x7fffffff;
 test = toString("\nMore testing: a = %d, %s\n", a, "This works too..");
 printf(test.c_str());

 a = 0x80000000;
 toString(test, "\nMore testing: a = %d, %s\n", a, "This way is cheaper");
 printf(test.c_str());

 return 0;
}
</code></pre>

String.h:

<pre><code>#pragma once
#include &lt;cstdarg&gt;
#include &lt;string&gt;

using ::std::string;

///
/// \breif Format message
/// \param dst String to store formatted message
/// \param format Format of message
/// \param ap Variable argument list
///
void toString(string &amp;dst, const char *format, va_list ap) throw();
///
/// \breif Format message
/// \param dst String to store formatted message
/// \param format Format of message
/// \param ... Variable argument list
///
void toString(string &amp;dst, const char *format, ...) throw();
///
/// \breif Format message
/// \param format Format of message
/// \param ... Variable argument list
///
string toString(const char *format, ...) throw();

///
/// \breif Format message
/// \param format Format of message
/// \param ap Variable argument list
///
string toString(const char *format, va_list ap) throw();
</code></pre>

blocks|key|1318751|text|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+%2B+1);
++++buf.resize(size);
++++snprintf(&buf[0],+size+%2B+1,+fmt,+args...);
++++return+buf;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1318752|使用C99+snprintf和C%2B%2B11|unstyled|1318753|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>template&lt;typename... Args&gt;
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(&amp;buf[0], size + 1, fmt, args...);
 return buf;
}
</code></pre>

Using C99 snprintf and C++11

blocks|key|1318774|text|这是可以试用的。很简单。但实际上并没有使用string类的细微差别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318775|#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+%25d",+100);
++++printf("%25s\n",+temp.c_str());

++++return+0;
}|code-block|syntax|javascript|1318776|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

this can be tried out. simple. really does not use nuances of the string class though.

<pre><code>#include &lt;stdarg.h&gt;
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;assert.h&gt;

#include &lt;string&gt;
#include &lt;exception&gt;
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(&amp;ptr, &amp;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;
}
</code></pre>

blocks|key|1318802|text|如果你在一个有asprintf(3)的系统上，你可以很容易地包装它：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1318803|#include+<iostream>
#include+<cstdarg>
#include+<cstdio>

std::string+format(const+char+*fmt,+...)+__attribute__+((format+(printf,+1,+2)));

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

++++va_list+ap;
++++va_start(ap,+fmt);

++++char+*tmp+=+0;
++++int+res+=+vasprintf(&tmp,+fmt,+ap);
++++va_end(ap);

++++if+(res+!=+-1)+{
++++++++result+=+tmp;
++++++++free(tmp);
++++}+else+{
++++++++//+The+vasprintf+call+failed,+either+do+nothing+and
++++++++//+fall+through+(will+return+empty+string)+or
++++++++//+throw+an+exception,+if+your+code+uses+those
++++}

++++return+result;
}

int+main(int+argc,+char+*argv[])+{
++++std::string+username+=+"you";
++++std::cout+<<+format("Hello+%25s!+%25d",+username.c_str(),+123)+<<+std::endl;
++++return+0;
}|code-block|syntax|javascript|1318804|entityMap|0|LINK|mutability|MUTABLE|url|http://linux.die.net/man/3/asprintf^0|7|B|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

If you are on a system that has <a href="http://linux.die.net/man/3/asprintf" rel="nofollow noreferrer">asprintf(3)</a>, you can easily wrap it:

<pre><code>#include &lt;iostream&gt;
#include &lt;cstdarg&gt;
#include &lt;cstdio&gt;

std::string format(const char *fmt, ...) __attribute__ ((format (printf, 1, 2)));

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

 va_list ap;
 va_start(ap, fmt);

 char *tmp = 0;
 int res = vasprintf(&amp;tmp, fmt, ap);
 va_end(ap);

 if (res != -1) {
 result = tmp;
 free(tmp);
 } else {
 // The vasprintf call failed, either do nothing and
 // fall through (will return empty string) or
 // throw an exception, if your code uses those
 }

 return result;
}

int main(int argc, char *argv[]) {
 std::string username = "you";
 std::cout &lt;&lt; format("Hello %s! %d", username.c_str(), 123) &lt;&lt; std::endl;
 return 0;
}
</code></pre>

blocks|key|1103914|text|为了以“sprintf”的方式格式化std::string，调用snprintf+(参数nullptr和0)来获取所需的缓冲区长度。使用C%2B%2B11可变模板编写函数，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1103915|#include+<cstdio>
#include+<string>
#include+<cassert>

template<+typename...+Args+>
std::string+string_sprintf(+const+char*+format,+Args...+args+)+{
++int+length+=+std::snprintf(+nullptr,+0,+format,+args...+);
++assert(+length+>=+0+);

++char*+buf+=+new+char[length+%2B+1];
++std::snprintf(+buf,+length+%2B+1,+format,+args...+);

++std::string+str(+buf+);
++delete[]+buf;
++return+str;
}|code-block|syntax|javascript|1103916|支持C%2B%2B11编译，例如在GCC中：g%2B%2B+-std=c%2B%2B11|1103917|用法：|1103918|++std::cout+<<+string_sprintf("%25g,+%25g\n",+1.23,+0.001);|1103919|entityMap^0|I|B|W|8|18|7|1G|1|0|0|I|E|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|15|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|R|$]]

In order to format <code>std::string</code> in a 'sprintf' manner, call <code>snprintf</code> (arguments <code>nullptr</code> and <code>0</code>) to get length of buffer needed. Write your function using C++11 variadic template like this:

<pre><code>#include &lt;cstdio&gt;
#include &lt;string&gt;
#include &lt;cassert&gt;

template&lt; typename... Args &gt;
std::string string_sprintf( const char* format, Args... args ) {
 int length = std::snprintf( nullptr, 0, format, args... );
 assert( length &gt;= 0 );

 char* buf = new char[length + 1];
 std::snprintf( buf, length + 1, format, args... );

 std::string str( buf );
 delete[] buf;
 return str;
}
</code></pre>

Compile with C++11 support, for example in GCC: <code>g++ -std=c++11</code>

Usage:

<pre><code> std::cout &lt;&lt; string_sprintf("%g, %g\n", 1.23, 0.001);
</code></pre>

blocks|key|1103943|text|_return.desc+=+(boost::format("fail+to+detect.+cv_result+=+%25d")+%25+st_result).str();|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1103944|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>_return.desc = (boost::format("fail to detect. cv_result = %d") % st_result).str();
</code></pre>

blocks|key|1103982|text|非常-非常简单的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1103983|std::string+strBuf;
strBuf.resize(256);
int+iCharsPrinted+=+sprintf_s((char+*)strPath.c_str(),+strPath.size(),+...);
strBuf.resize(iCharsPrinted);|code-block|syntax|javascript|1103984|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Very-very simple solution.

<pre><code>std::string strBuf;
strBuf.resize(256);
int iCharsPrinted = sprintf_s((char *)strPath.c_str(), strPath.size(), ...);
strBuf.resize(iCharsPrinted);
</code></pre>

blocks|key|1104034|text|我通常这样用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1104035|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;
}|code-block|syntax|javascript|1104036|缺点:并非所有系统都支持vasprint|1104037|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I usually use this:

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

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

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

 return result;
}
</code></pre>

Disadvantage: not all systems support vasprint

blocks|key|1104084|text|下面略微修改了@iFreilicht+answer的版本，更新为C%2B%2B14+(使用make_unique函数而不是原始声明)，并添加了对std::string参数的支持(基于Kenny+Kerr+article)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1104085|#include+<iostream>
#include+<memory>
#include+<string>
#include+<cstdio>

template+<typename+T>
T+process_arg(T+value)+noexcept
{
++++return+value;
}

template+<typename+T>
T+const+*+process_arg(std::basic_string<T>+const+&+value)+noexcept
{
++++return+value.c_str();
}

template<typename+...+Args>
std::string+string_format(const+std::string&+format,+Args+const+&+...+args)
{
++++const+auto+fmt+=+format.c_str();
++++const+size_t+size+=+std::snprintf(nullptr,+0,+fmt,+process_arg(args)+...)+%2B+1;
++++auto+buf+=+std::make_unique<char[]>(size);
++++std::snprintf(buf.get(),+size,+fmt,+process_arg(args)+...);
++++auto+res+=+std::string(buf.get(),+buf.get()+%2B+size+-+1);
++++return+res;
}

int+main()
{
++++int+i+=+3;
++++float+f+=+5.f;
++++char*+s0+=+"hello";
++++std::string+s1+=+"world";
++++std::cout+<<+string_format("i=%25d,+f=%25f,+s=%25s+%25s",+i,+f,+s0,+s1)+<<+"\n";
}|code-block|syntax|javascript|1104086|输出：|1104087|i+=+3,+f+=+5.000000,+s+=+hello+world|1104088|如果需要，可以将此答案与原始答案合并。|1104089|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/C%252B%252B14|1|https://msdn.microsoft.com/en-us/magazine/dn913181.aspx^0|15|B|1W|B|W|5|0|2Q|7|1|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]|$9|18|A|19|1|1A]]|E|$]]|$1|F|3|G|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1C|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1D|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1E|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

Below slightly modified version of @iFreilicht answer, updated to <a href="https://en.wikipedia.org/wiki/C%2B%2B14" rel="nofollow">C++14</a> (usage of <code>make_unique</code> function instead of raw declaration) and added support for <code>std::string</code> arguments (based on Kenny Kerr <a href="https://msdn.microsoft.com/en-us/magazine/dn913181.aspx" rel="nofollow">article</a>)

<pre><code>#include &lt;iostream&gt;
#include &lt;memory&gt;
#include &lt;string&gt;
#include &lt;cstdio&gt;

template &lt;typename T&gt;
T process_arg(T value) noexcept
{
 return value;
}

template &lt;typename T&gt;
T const * process_arg(std::basic_string&lt;T&gt; const &amp; value) noexcept
{
 return value.c_str();
}

template&lt;typename ... Args&gt;
std::string string_format(const std::string&amp; format, Args const &amp; ... args)
{
 const auto fmt = format.c_str();
 const size_t size = std::snprintf(nullptr, 0, fmt, process_arg(args) ...) + 1;
 auto buf = std::make_unique&lt;char[]&gt;(size);
 std::snprintf(buf.get(), size, fmt, process_arg(args) ...);
 auto res = std::string(buf.get(), buf.get() + size - 1);
 return res;
}

int main()
{
 int i = 3;
 float f = 5.f;
 char* s0 = "hello";
 std::string s1 = "world";
 std::cout &lt;&lt; string_format("i=%d, f=%f, s=%s %s", i, f, s0, s1) &lt;&lt; "\n";
}
</code></pre>

Output:

<pre><code>i = 3, f = 5.000000, s = hello world
</code></pre>

Feel free to merge this answer with the original one if desired.

blocks|key|1104125|text|我知道这个问题已经回答过很多次了，但这句话更简洁：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1104126|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());
}|code-block|syntax|javascript|1104127|示例：|1104128|#include+<iostream>
#include+<random>

int+main()
{
++++std::random_device+r;
++++std::cout+<<+format("Hello+%25d!\n",+r());
}|1104129|另请参阅http://rextester.com/NJB14150|offset|length|1104130|entityMap|0|LINK|mutability|MUTABLE|url|http://rextester.com/NJB14150^0|0|0|0|0|4|T|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|10|8|@]|9|@$M|11|N|12|1|13]]|A|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

I realize this has been answered many times, but this is more concise:

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

example:

<pre><code>#include &lt;iostream&gt;
#include &lt;random&gt;

int main()
{
 std::random_device r;
 std::cout &lt;&lt; format("Hello %d!\n", r());
}
</code></pre>

See also <a href="http://rextester.com/NJB14150" rel="nofollow noreferrer">http://rextester.com/NJB14150</a>

blocks|key|1104169|text|更新了一些答案，不同之处在于-函数将正确接受%25s的std：：字符串|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1104170|namespace+format_helper
{

++++template+<class+Src>
++++inline+Src+cast(Src+v)
++++{
++++++++return+v;
++++}

++++inline+const+char+*cast(const+std::string&+v)
++++{
++++++++return+v.c_str();
++++}
};

template+<typename...+Ts>
inline+std::string+stringfmt+(const+std::string+&fmt,+Ts&&...+vs)
{
++++using+namespace+format_helper;
++++char+b;
++++size_t+required+=+std::snprintf(&b,+0,+fmt.c_str(),+cast(std::forward<Ts>(vs))...);//not+counting+the+terminating+null+character.
++++std::string+result;
++++//because+we+use+string+as+container,+it+adds+extra+0+automatically
++++result.resize(required+,+0);
++++//and+snprintf+will+use+n-1+bytes+supplied
++++std::snprintf(const_cast<char*>(result.data()),+required+%2B+1,+fmt.c_str(),+cast(std::forward<Ts>(vs))...);

++++return+result;
}|code-block|syntax|javascript|1104171|直播：http://cpp.sh/5ajsv|offset|length|1104172|entityMap|0|LINK|mutability|MUTABLE|url|http://cpp.sh/5ajsv^0|0|0|3|J|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Update of some answer around, difference is - function will properly accept std::string for %s

<pre><code>namespace format_helper
{

 template &lt;class Src&gt;
 inline Src cast(Src v)
 {
 return v;
 }

 inline const char *cast(const std::string&amp; v)
 {
 return v.c_str();
 }
};

template &lt;typename... Ts&gt;
inline std::string stringfmt (const std::string &amp;fmt, Ts&amp;&amp;... vs)
{
 using namespace format_helper;
 char b;
 size_t required = std::snprintf(&amp;b, 0, fmt.c_str(), cast(std::forward&lt;Ts&gt;(vs))...);//not counting the terminating null character.
 std::string result;
 //because we use string as container, it adds extra 0 automatically
 result.resize(required , 0);
 //and snprintf will use n-1 bytes supplied
 std::snprintf(const_cast&lt;char*&gt;(result.data()), required + 1, fmt.c_str(), cast(std::forward&lt;Ts&gt;(vs))...);

 return result;
}
</code></pre>

Live: <a href="http://cpp.sh/5ajsv" rel="nofollow noreferrer">http://cpp.sh/5ajsv</a>

blocks|key|1319113|text|这是一个特定于Windows的解决方案，旨在避免Visual+Studio中的编译器警告，而不会使它们静默。有问题的警告是使用带有va_start的std::string，这会错误地产生警告，以及使用不推荐使用的printf变体。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1319114|template<typename+...+va>
std::string+Format(+const+std::string&+format,+va+...+args+)
{
++++std::string+s;
++++s.resize(+_scprintf(+format.c_str(),+args+...+)+%2B+1+);
++++s.resize(+_snprintf_s(+s.data(),+s.capacity(),+_TRUNCATE,+format.c_str(),+args+...+)+);
++++return+s;
}

template<typename+...+va>
std::wstring+Format(+const+std::wstring&+format,+va+...+args+)
{
++++std::wstring+s;
++++s.resize(+_scwprintf(+format.c_str(),+args+...+)+%2B+1+);
++++s.resize(+_snwprintf_s(+s.data(),+s.capacity(),+_TRUNCATE,+format.c_str(),+args+...+)+);
++++return+s;
}

std::string+s+=+Format(+"%25hs+%25d",+"abc",+123+);
std::wstring+ws+=+Format(+L"%25hs+%25d",+"abc",+123+);|code-block|syntax|javascript|1319115|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This is a Windows specific solution designed to avoid compiler warnings in Visual Studio without silencing them. The warnings in question are for using an std::string with va_start, which produces a warning erroneously, and for using deprecated printf variants. 

<pre><code>template&lt;typename ... va&gt;
std::string Format( const std::string&amp; format, va ... args )
{
 std::string s;
 s.resize( _scprintf( format.c_str(), args ... ) + 1 );
 s.resize( _snprintf_s( s.data(), s.capacity(), _TRUNCATE, format.c_str(), args ... ) );
 return s;
}

template&lt;typename ... va&gt;
std::wstring Format( const std::wstring&amp; format, va ... args )
{
 std::wstring s;
 s.resize( _scwprintf( format.c_str(), args ... ) + 1 );
 s.resize( _snwprintf_s( s.data(), s.capacity(), _TRUNCATE, format.c_str(), args ... ) );
 return s;
}

std::string s = Format( "%hs %d", "abc", 123 );
std::wstring ws = Format( L"%hs %d", "abc", 123 );
</code></pre>

blocks|key|1104257|text|我现在将为Visual+Studio编写版本，希望有一天有人会让它变得可移植。(疑似需要用vsnwprintf或类似的东西替换_vsnwprintf。)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1104258|您需要通过在项目配置中使用define+_CRT_SECURE_NO_WARNINGS来禁用弃用警告。|1104259|我使用带有第一个参数的_vsnwprintf作为nullptr，以便能够估计缓冲区大小，保留wstring缓冲区，然后将字符串直接格式化为缓冲区。|1104260|不确定为什么需要禁用弃用警告，因为同一方法调用(_vsnwprintf_s)的安全版本不能使用nullptr作为输入。需要向微软C%2B%2B团队报告可疑情况。|1104261|这个版本应该可以同时使用-+string或wstring类。|1104262|如果您发现任何错误或不一致，请再次询问，我将尝试修复它。|1104263|stringHelpers.h:

#pragma+once
#include+<string>

//
//++Formats+string/wstring+according+to+format,+if+formatting+fails+(e.g.+invalid+%25s+pointer+-+returns+empty+string)
//
template+<typename+T>
std::basic_string<T>+sFormat(const+T*+format,+...)
{
++++va_list+args;
++++va_start(args,+format);
++++int+size;

++++if+constexpr+(std::is_same_v<T,+char>)
++++++++size+=+vsnprintf(nullptr,+0,+format,+args);
++++else
++++++++size+=+_vsnwprintf(nullptr,+0,+format,+args);

++++size%2B%2B;+//+Zero+termination
++++std::basic_string<T>+s;
++++s.resize(size);

++++if+constexpr+(std::is_same_v<T,+char>)
++++++++vsnprintf(&s[0],+size,+format,+args);
++++else
++++++++_vsnwprintf(&s[0],+size,+format,+args);

++++va_end(args);
++++return+s;
}|code-block|syntax|javascript|1104264|上面是代码示例，可以直接复制。我将在github中维护我自己的存储库中的工作版本：|1104265|https://github.com/tapika/cppscriptcore/blob/master/SolutionProjectModel/helpers.h#L12|1104266|entityMap|0|LINK|mutability|MUTABLE|url^0|19|A|1R|B|0|K|N|0|B|B|O|7|0|O|D|1B|7|0|E|6|L|7|0|0|0|0|0|2E|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|1D|8|@$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|L|3|M|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]]|D|@]|E|$]]|$1|N|3|O|5|6|7|1S|8|@]|D|@]|E|$]]|$1|P|3|Q|5|R|7|1T|8|@]|D|@]|E|$S|T]]|$1|U|3|V|5|6|7|1U|8|@]|D|@]|E|$]]|$1|W|3|X|5|6|7|1V|8|@]|D|@$9|1W|A|1X|1|1Y]]|E|$]]|$1|Y|3|-4|5|6|7|1Z|8|@]|D|@]|E|$]]]|Z|$10|$5|11|12|13|E|$14|X]]]]

I will now write version for Visual Studio, hopefully someday someone will make it portable. (Suspect need to replace <code>_vsnwprintf</code> with <code>vsnwprintf</code> and something like this.)

You need to disable deprecate warnings by using define <code>_CRT_SECURE_NO_WARNINGS</code> from project configuration.

I'm using <code>_vsnwprintf</code> with first parameter as a <code>nullptr</code> to be able to estimate buffer size, reserve wstring buffer, and then formatting string directly into buffer.

Not sure why you need to disable deprecated warning, as safe versions of same method call (<code>_vsnwprintf_s</code>) cannot use <code>nullptr</code> as an input. Suspect needs to be reported to Microsoft C++ team.

This version should be working with both - <code>string</code> or <code>wstring</code> classes.

If you find any bug or inconsistency, please ask again, I'll try to fix it.

<pre><code>stringHelpers.h:

#pragma once
#include &lt;string&gt;

//
// Formats string/wstring according to format, if formatting fails (e.g. invalid %s pointer - returns empty string)
//
template &lt;typename T&gt;
std::basic_string&lt;T&gt; sFormat(const T* format, ...)
{
 va_list args;
 va_start(args, format);
 int size;

 if constexpr (std::is_same_v&lt;T, char&gt;)
 size = vsnprintf(nullptr, 0, format, args);
 else
 size = _vsnwprintf(nullptr, 0, format, args);

 size++; // Zero termination
 std::basic_string&lt;T&gt; s;
 s.resize(size);

 if constexpr (std::is_same_v&lt;T, char&gt;)
 vsnprintf(&amp;s[0], size, format, args);
 else
 _vsnwprintf(&amp;s[0], size, format, args);

 va_end(args);
 return s;
}
</code></pre>

Above is sample of code, which can be copied as such. I will maintain working version in my own repository in github:

<a href="https://github.com/tapika/cppscriptcore/blob/master/SolutionProjectModel/helpers.h#L12" rel="nofollow noreferrer">https://github.com/tapika/cppscriptcore/blob/master/SolutionProjectModel/helpers.h#L12</a>

blocks|key|1319195|text|Windows和Visual+Studio有一个极具吸引力的解决方案:+CString。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1319196|CString+str;
str.Format("Hello+%25s\n",+"World");
str+=+"ABC";
str+%2B=+"DEF";|code-block|syntax|javascript|1319197|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Windows and Visual Studio have a mighty attractive solution: CString.

<pre><code>CString str;
str.Format("Hello %s\n", "World");
str = "ABC";
str += "DEF";
</code></pre>

blocks|key|1319228|text|这个问题已经解决了。但是，我认为这是在c%2B%2B中使用format+string的另一种方式|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1319229|class+string_format+{
private:
++++std::string+_result;
public:
++++string_format(+)+{+}
++++~string_format(+)+{+std::string(+).swap(+_result+);+}
++++const+std::string&+get_data(+)+const+{+return+_result;+}
++++template<typename+T,+typename...+Targs>
++++void+format(+const+char*+fmt,+T+value,+Targs...+Fargs+)+{
++++++++for+(+;+*fmt+!=+'\0';+fmt%2B%2B+)+{
++++++++++++if+(+*fmt+==+'%25'+)+{
++++++++++++++++_result+%2B=+value;
++++++++++++++++this->format(+fmt+%2B+1,+Fargs...,+0+);+//+recursive+call
++++++++++++++++return;
++++++++++++}
++++++++++++_result+%2B=+*fmt;
++++++++}
++++}
++++friend+std::ostream&+operator<<(+std::ostream&+ostream,+const+string_format&+inst+);
};
inline+std::string&+operator%2B=(+std::string&+str,+int+val+)+{
++++str.append(+std::to_string(+val+)+);
++++return+str;
}
inline+std::string&+operator%2B=(+std::string&+str,+double+val+)+{
++++str.append(+std::to_string(+val+)+);
++++return+str;
}
inline+std::string&+operator%2B=(+std::string&+str,+bool+val+)+{
++++str.append(+val+?+"true"+:+"false"+);
++++return+str;
}
inline+std::ostream&+operator<<(+std::ostream&+ostream,+const+string_format&+inst+)+{
++++ostream+<<+inst.get_data(+);
++++return+ostream;
}|code-block|syntax|javascript|1319230|并像这样测试这个类：|1319231|string_format+fmt;
fmt.format(+"Hello+%25+and+is+working+?+Ans:+%25",+"world",+true+);
std::cout+<<+fmt;|1319232|你可以在here上查看|1319233|entityMap|0|LINK|mutability|MUTABLE|url|http://cpp.sh/4knm2^0|J|3|P|D|0|0|0|0|4|4|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]]|E|$]]|$1|Q|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

This question already solved. But, I think this is another way to <code>format string</code> in <code>c++</code>
<pre><code>class string_format {
private:
 std::string _result;
public:
 string_format( ) { }
 ~string_format( ) { std::string( ).swap( _result ); }
 const std::string&amp; get_data( ) const { return _result; }
 template&lt;typename T, typename... Targs&gt;
 void format( const char* fmt, T value, Targs... Fargs ) {
 for ( ; *fmt != '\0'; fmt++ ) {
 if ( *fmt == '%' ) {
 _result += value;
 this-&gt;format( fmt + 1, Fargs..., 0 ); // recursive call
 return;
 }
 _result += *fmt;
 }
 }
 friend std::ostream&amp; operator&lt;&lt;( std::ostream&amp; ostream, const string_format&amp; inst );
};
inline std::string&amp; operator+=( std::string&amp; str, int val ) {
 str.append( std::to_string( val ) );
 return str;
}
inline std::string&amp; operator+=( std::string&amp; str, double val ) {
 str.append( std::to_string( val ) );
 return str;
}
inline std::string&amp; operator+=( std::string&amp; str, bool val ) {
 str.append( val ? &quot;true&quot; : &quot;false&quot; );
 return str;
}
inline std::ostream&amp; operator&lt;&lt;( std::ostream&amp; ostream, const string_format&amp; inst ) {
 ostream &lt;&lt; inst.get_data( );
 return ostream;
}
</code></pre>
and test this class as:
<pre><code>string_format fmt;
fmt.format( &quot;Hello % and is working ? Ans: %&quot;, &quot;world&quot;, true );
std::cout &lt;&lt; fmt;
</code></pre>
and you may check it <a href="http://cpp.sh/4knm2" rel="nofollow noreferrer">here</a>

I have to format <a href="http://en.cppreference.com/w/cpp/string/basic_string"><code>std::string</code></a> with <a href="http://en.cppreference.com/w/cpp/io/c/fprintf"><code>sprintf</code></a> and send it into file stream. How can I do this?

std::string formatting like sprintf

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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问std：：字符串格式，如sprintf
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