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C++ Discussion Thread
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Jan 27th, 2009

write() function...

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good day everyone.. thx for reading..

this is my problem:
i want to use the write() function, in ofstream, to write strings into a file.. but write() requires parameters of const char pointer and streamsize...

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for(unsigned i=0; i != questions.size(); i++)
	{
		qptr = &questions[i]; 		//vector element(string)
		tempfile.write(qptr, stringsize);
	}

do i really need to convert string to char first? any simpler way?

and,, any better idea than using write()??

thx..

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azwraith69

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Jan 27th, 2009

Re: write() function...

If you're talking about std::strings you could use the c_str() method?

(I'm assuming "questions" is a vector of std::strings)

C++ Syntax (Toggle Plain Text)
tempfile.write(questions[i].c_str(), questions[i].size());
tempfile.write(questions[i].c_str(), questions[i].size());

But if tempfile is an ofstream, why not use the << operator?

C++ Syntax (Toggle Plain Text)
ofstream tempfile("yourfilename_goes_here");
std::string foo = "bar";
tempfile << foo;
ofstream tempfile("yourfilename_goes_here");
std::string foo = "bar";
tempfile << foo;

Nick Evan

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Jan 28th, 2009

Re: write() function...

Click to Expand / Collapse Quote originally posted by niek_e ...

If you're talking about std::strings you could use the c_str() method?

(I'm assuming "questions" is a vector of std::strings)
C++ Syntax (Toggle Plain Text)
tempfile.write(questions[i].c_str(), questions[i].size());
tempfile.write(questions[i].c_str(), questions[i].size());
But if tempfile is an ofstream, why not use the << operator?
C++ Syntax (Toggle Plain Text)
ofstream tempfile("yourfilename_goes_here");
std::string foo = "bar";
tempfile << foo;
ofstream tempfile("yourfilename_goes_here"); std::string foo = "bar"; tempfile << foo;

ofstream,, so i can't use the 1st one..

my strings in the vectors have white spaces.. i think << stops on white spaces,, correct me if i'm wrong,, so can't use that one..

thx for help..

any other ideas?? i'll try to use write() for now,, converting my strings to char.. but any better ideas will help..

thx

azwraith69

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Jan 28th, 2009

Re: write() function...

Click to Expand / Collapse Quote originally posted by azwraith69 ...

i'll try to use write() for now,, converting my strings to char.. but any better ideas will help..

that's what option 1 does

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Re: write() function...

C++ Syntax (Toggle Plain Text)
#include <fstream>
#include <string>
 
int main(int argc, char *argv[]){
    std::string example = "Hello, world!\nHow are you?\n\tSuper thanks!";
    std::ofstream exfile("test.txt");
 
    if(!exfile.good()) return 0;
    exfile << example;
 
    exfile.close();
    return 0;
}
#include <fstream>
#include <string>

int main(int argc, char *argv[]){
    std::string example = "Hello, world!\nHow are you?\n\tSuper thanks!";
    std::ofstream exfile("test.txt");
    
    if(!exfile.good()) return 0;
    exfile << example;
    
    exfile.close();
    return 0;
}

I see no whitespace problem...

C++ Syntax (Toggle Plain Text)

Hello, world!
How are you?
	Super thanks!

Chris

Last edited by Freaky_Chris; Jan 28th, 2009 at 5:51 am.

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Jan 28th, 2009

Re: write() function...

ok,, thx for everything..

i thought << operator in ofstream is the same as << operator in cout... now i knew it doesn't stop at white spaces..

thx again!

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