I always forget how to use boost::format when I need it. So, here are a few samples from when I did remember.

Only need is to include the proper boost header. No compile of any of the boost libraries is necessary.

The source is also available in subversion (webclient) (subversion checkout).

// build with make or:
//
// g++ -I../../boost_1_46_0 fmt.cpp
//

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

using namespace std;
using namespace boost;

int main()
{
    stringstream ss;

    int year    = 2011;
    int month   = 3;
    int day     = 11;
    int hour    = 12;
    int minute  = 1;
    double seconds= 23.35;
    double epoch  = 1231234567890.35;

    // Fill with whitespace, right align
    ss << format("#1.0 %4i %4i %4i\n") % year % month % day;
    // Output: #1.0 2011    3   11

    // Fill with whitespace, left align
    ss << format("#1.1 %-4i %-4i %-4i\n") % year % month % day;
    // Output: #1.1 2011 3    11

    // Fill with zero (pad)
    ss << format("#2.0 %04i %04i %04i\n") % year % month % day;
    // Output: #2.0 2011 0003 0011

    // Floating point precision
    ss << format("#3.0 %11.2f\n") % seconds;
    // Output: #3.0       23.35

    // Floating point precision with zero-fill (zero pad)
    ss << format("#4.0 %011.2f\n") % seconds;
    // Output: #4.0 00000023.35

    // Left aligned string literal with 30+20 columns
    ss << format("#5.0 %-30s%-20s\n") % "LEFT ALIGNED 1" % "LEFT ALIGNED 2";
    // Output: #5.0 LEFT ALIGNED 1                LEFT ALIGNED 2

    // Right aligned string literal
    ss << format("#6.0 %30s%20s\n") % "RIGHT ALIGNED 1" % "RIGHT ALIGNED 2";
    // Output: #6.0                RIGHT ALIGNED 1     RIGHT ALIGNED 2

    cout << ss.str();

    return 0;
}

The output should be:

#1.0 2011    3   11
#1.1 2011 3    11
#2.0 2011 0003 0011
#3.0       23.35
#4.0 00000023.35
#5.0 LEFT ALIGNED 1                LEFT ALIGNED 2
#6.0                RIGHT ALIGNED 1     RIGHT ALIGNED 2