file i/o problems

[iamthejake2000]

i'm new to c++ and i'm trying to get a hang of file i/o. this code is making errors when i try to compile it (main() is yet to be filled):

#include <string>
#include <iostream>
#include <fstream>

using namespace std;

void lfuncWrite(string lsFiletowrite, string lsContentstowrite)
{
	ofstream File(lsFiletowrite); //load for output (writing) and delete contents.
	File << lsContentstowrite;    //write.
	cout << "Done.";
}


void lfuncRead(string lsFiletoread)
{
	string lsFilecontents;

	ifstream File(lsFiletoread);
	File >> lsFilecontents;
	cout << lsFilecontents;
}


int main()
{


	return 0;
}

i'm using visual c++ pro by the way.

thanks.

[Nazca]

I was under the impression you could not use a string to name a file to read (or dynamically select a file in any way). I may be wrong, but I've tried it myself and failed miserably.
I used Perl instead - it worked a lot better.

[JoshR]

Read up on fstream

you need to change the string to a c style string
like this:

void lfuncWrite(string lsFiletowrite, string lsContentstowrite)
{
        ofstream File;
        char* fn = lsFiletowrite.c_str();

	File.open(fn); //load for output (writing) and delete contents.
	File << lsContentstowrite;    //write.
        File.close();  //close the file when done
	cout << "Done.";
}

[iamthejake2000]

is there a way to let the user input a file name in c++?

[JoshR]

ya
you can just get input to the string, then run the string through your function.

for example:

string fileNameOutput, content;

cout << "Enter file name for output:";
cin >> fileNameOutput;
cin.get();
cout << "Enter content:";
getline(cin, content);

void lfuncWrite(fileNameOutput, content);

[Daved]

Read up on fstream

you need to change the string to a c style string
like this:

 
void lfuncWrite(string lsFiletowrite, string lsContentstowrite)
{
	ofstream File;
	char* fn = lsFiletowrite.c_str();
 
	File.open(fn); //load for output (writing) and delete contents.
	File << lsContentstowrite; //write.
	File.close(); //close the file when done
	cout << "Done.";
}

JoshR, the changes you made are not necessary, I assume/hope you only did them to show what is going on.

void lfuncWrite(string lsFiletowrite, string lsContentstowrite)
{
	ofstream File(lsFiletowrite.c_str()); //load for output (writing) and delete contents.
	File << lsContentstowrite;	//write.
	cout << "Done.";
}

iamthejake2000, The code in red is all you need.

[JoshR]

ya just showing how you have a pointer to assign a string to it (in style) because thats what it has to be to pass through the open command

you could obviously substitute lsFiletowrite.c_str() instead of fn in the open command

[Daved]

In addition, you don't need the explicit calls to open and close, and you should be using a const char* since that is what c_str() returns.

[JoshR]

True, but you can open and close it at different times, for example if your reading from a file and you encounter a specific character you can close it before finishing through all the characters.

I used it to show exactly whats going on.

Closing a file sets the eof marker so if you were using it then you wanted to open it to read from it, you should close it before re-opening it.