Writing to input and output files in c++

Question

I cannot get my code to compile because it keeps telling me "error: no matching function for call" on line 16. Any advice? I am suppose to read the file and write all the vowels to an output file.

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main(){
    string filename;    // to hold the file name
    ifstream inputfile; // input to a file


    // Get the file name
    cout << "Enter a file name: ";
    cin >> filename;

    // Open the file
    inputfile.open(filename); // LINE 16

    char vowel; // to store the vowels
    ofstream outputfile; // to write to the file

    // open file
    outputfile.open("vowels_.txt");

    while(inputfile.get(vowel)){
        //If the char is a vowel or newline, write to output file.
        if((vowel == 'a')||(vowel == 'A')||(vowel =='e')||(vowel =='E')||(vowel =='i')||(vowel =='I')||(vowel =='o')||(vowel =='O')||(vowel =='u')||(vowel =='U')||(vowel =='\n') && !inputfile.eof())
            outputfile.put(vowel);

    }

    inputfile.close();
    outputfile.close();



}

I guess it is the open() call. You need to pass a character pointer, like: `inputfile.open(filename.c_str());` — Rene, Sep 13 '17 at 05:36

gsamaras · Accepted Answer · 2017-09-13T06:03:15.150

2

Change this:

inputfile.open(filename);

to this:

inputfile.open(filename.c_str());

since filename is an std::string, and fstream::open takes const char* filename as a parameter.

Calling string:c_str returns const char* from std::string.

C++11 does not need this, since fstream::open is overloaded to take an std::string as well. Compile with -std=c++11 flag to enable c++11.

PS: Why don't the std::fstream classes take a std::string? (Pre-C++1)

edited Sep 13 '17 at 06:03

answered Sep 13 '17 at 05:37

gsamaras

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OH OKAY. THANK YOU – Sep 13 '17 at 05:40
how do i do that? – Sep 13 '17 at 05:42
Any insight on *why* you can't use `std::string`? – Passer By Sep 13 '17 at 05:47
@PasserBy you mean with `fstream::open`? It has to do with the function's prototype, pre-C++11 and post. – gsamaras Sep 13 '17 at 05:54
Yes, but I meant what was the original consideration that made it lack such an overload? – Passer By Sep 13 '17 at 06:02

Writing to input and output files in c++

1 Answers1