CODEWITHSUNDEEP
c++gccwindows-7
Vlassis Fotis
Vlassis Fotis

Reputation: 47

writing in a user-defined .txt file

The basic syntax I use to write to a .txt file is this:

ofstream myfile;
myfile.open ("data.txt", ios::trunc);
outfile<<"writing";

Now, supposing i were to let the user decide which file should be accessed, could it be done through a string?

#include <iostream>
#include <fstream>
using namespace std;
int main (){
    ofstream myfile;
    string filename;
    char x;
    cin>>x;
    if (x==1)
        filename="data2.txt";
    myfile.open (filename, ios::trunc);
    myfile<<"writing";
    return 0;
}

I already tested this and it didn't work. My question is: is it possible to do such a thing? If yes, how? When i compile it, the error i get is the following:

undefined reference to 'std::basicofstream<char, std::char_traits<char> >::open(std::string const&, std::_Ios_Openmode)'

I can't understand what it is that's causing it.

Upvotes: 0

Views: 422

Answers (2)

Thomas Matthews
Thomas Matthews

Reputation: 57728

Your error says it can't find open method that uses std::string.

Try this:

myfile.open(filename.c_str(), ios::trunc);

Some versions of C++ do not allow the std::string for open method, so you will have to use the c_str() method of std::string.

Upvotes: 2

ForceBru
ForceBru

Reputation: 44878

You should add an else branch since if x isn't equal to 1 open has nothing to open.

Also you forgot to declare ofstream myfile; in your second snippet. Maybe that's the reason this doesn't work (it shouldn't even compile).

Upvotes: 1

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