Re: [Boost-users] [string] HowTo: equiv of printf("%.5s\n", myBuf10);

10 Apr 2006


      This seems to work ok using boost::format:

#include <iostream>
#include 
void main(void)
{
   std::string myBuf10("1234567890");
   std::cout << "Put truncated: "
          << boost::format("%|.5s|\n") % myBuf10
          << " part of " << myBuf10 << std::endl;
}

----- Original Message ----- 
From: "Lynn Allan" 
Newsgroups: gmane.comp.lib.boost.user
Sent: Saturday, April 08, 2006 11:07 AM
Subject: [string] HowTo: equiv of printf("%.5s\n", myBuf10);
...
I've been puzzled about doing the equivalent of:
printf("%.5s\n", myBuf10);
and also:
printf("%.*s\n", 5, myBuf10);
std::string myBuf10("0123456789");
const char* pBuf = myBuf10.c_str();
printf("%.5s\n", pBuf);
printf("%.*s\n", 5, pBuf);
cout << myBuf10.substr(0, 5) << endl;    // works ok -> 01234
cout << setw(5) << myBuf10 << endl;    // 0123456789
I've used:
myBuf10.substr(0, 5);
and also ostringstream
but it seems like there might be a simpler way. setw(5) doesn't work to 
accomplish truncation (at least for me). It seems more for padding. Am I 
unaware of some iomanip functionality to accomplish this?
I suppose I could do something like:
char hack = myBuf[5];
myBuf[5] = '\0';
.... do something
myBuf[5] = hack;
(may or may not be portable?)
Note: newbie with std::string ... using Microsoft vc7.1 compiler
Thanks.