Thread: Format string in C++

Hello,

I would like to know how to format strings in C++ like the string.Format from C#. I think sprintf it is only usable with chars, which is not the case. I tried boost with the following code:

Code:

const std::string ProcInfoParser::statmPath = "/proc/%1%/statm";

void ProcInfoParser::gatherMemoryUsage(int _processPid) {


    std::string path;

    cout << boost::format("/proc/%1%/statm") % _processPid;


    std::string data;
    data = parseData(path);


    return;
}

But no success, as I got the following errors:

Code:

../src/parser/ProcInfoParser.cpp: In member function ‘void ProcInfoParser::gatherMemoryUsage(int)’:
../src/parser/ProcInfoParser.cpp:32: error: no matching function for call to ‘std::basic_string<char, std::char_traits<char>, std::allocator<char> >::append(boost::basic_format<char, std::char_traits<char>, std::allocator<char> >&)’
/usr/include/c++/4.4/bits/basic_string.tcc:325: note: candidates are: std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::append(const std::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]
/usr/include/c++/4.4/bits/basic_string.tcc:342: note:                 std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::append(const std::basic_string<_CharT, _Traits, _Alloc>&, typename _Alloc::rebind<_CharT>::other::size_type, typename _Alloc::rebind<_CharT>::other::size_type) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]
/usr/include/c++/4.4/bits/basic_string.tcc:298: note:                 std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::append(const _CharT*, typename _Alloc::rebind<_CharT>::other::size_type) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]
/usr/include/c++/4.4/bits/basic_string.h:863: note:                 std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::append(const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]
/usr/include/c++/4.4/bits/basic_string.tcc:281: note:                 std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::append(typename _Alloc::rebind<_CharT>::other::size_type, _CharT) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]
make: *** [src/parser/ProcInfoParser.o] Error 1

How should I proceed?

Pedro

Ok, your exemple also compiles for me. But the following no:

Code:

#include <iostream>
#include <boost/format.hpp>


void gatherMemoryUsage(int processPid)
{
	std::string a;
    a << boost::format("/proc/%1%/statm") % processPid;
}


int main()
{
    gatherMemoryUsage(1);
}

The problem is in the assignment of the string. How does it work in c++? I tried using string.append but it also does not work, and string << boost:: [...] also does not.

Thanks!

you can use a std::stringstream for this. it works exactly like cin/cout, except it stores its data in a string, instead of reading/writing the console.

Code:

#include <iostream>
#include <sstream>
#include <boost/format.hpp>
 
 
void gatherMemoryUsage(int processPid)
{
    std::stringstream ss;
    ss << boost::format("/proc/%1%/statm") % processPid;
    std::string a = ss.str();
}
 
 
int main()
{
    gatherMemoryUsage(1);
}