extract from string and put into a file

bluefish (2)
Hi all,

I'm learning C++, and I got a problem. I found a code in cplusplus, that extract part of the string.
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void extract(char *s,char *t,char *d,int pos,int len)
{
s=s+(pos-1);
t=s+len;

while(s!=t)
{
*d=*s;
s++;
d++;
}
*d='\0';

}

I want to put what I extracted into a textfile. I tried, but the text file awlays blank. Please help me. Thank you all.
Cubbi (4774)
That's a poorly written C function. If you're really learning C++, you should do it this way:

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#include <fstream>
#include <iostream>
#include <string>
using namespace std;
std::string extract(const std::string src, int pos, int len)
{
    return src.substr(pos, len);
}
int main()
{
    std::cout << extract("Hello, world", 3, 2) << '\n';
    // or, to a file
    std::ofstream f("test.out");
    f << extract("Hello, world", 2, 3) << '\n';
}
Last edited on
bluefish (2)
Thank you so much. I'll try again.
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