opening files

[Tim Baker]

Hi,
I'm trying to master the basics of file operations, but am coming up with a
problem.
The code below should request a file to open, then report whether it was
successful in opening or not. When I try to compile it it seems that the
ifstream fuction is being passed a pointer to the string rather than the
string itself. I tried putting &s and *s ion various places, but to no
avail. Can someone tell me what I'm doing wrong?

thanks,
Tim

******* Testfile.cpp*******


#include <stdio.h>
#include <iostream.h>
#include <fstream.h>
#include <string>

int main(int nNumArgs, char* pzArgs[])
{
string filename;
cout << "What file do you want to open?\n";
cin >> filename;

ifstream inputFile(filename, ios::nocreate);
if (inputFile.bad())
{
cout << "Couldn't find that file\n"
<< "Please check the filename and try again\n";
}

else
{
cout << "hooray, you opened " << filename << " like a pro\n";
}
inputFile.close();
}

 

[Tim Love]

Hi,
I'm trying to master the basics of file operations, but am coming up with a
problem.
The code below should request a file to open, then report whether it was
successful in opening or not. When I try to compile it it seems that the
ifstream fuction is being passed a pointer to the string rather than the
string itself. I tried putting &s and *s ion various places, but to no
avail. Can someone tell me what I'm doing wrong?

In
ifstream inputFile(filename, ios::nocreate);
your filename is a string instead of the required "const char *" so
try
ifstream inputFile(filename.c_str(), ios::nocreate);
instead.

Also consider replacing

#include <stdio.h>
#include <iostream.h>
#include <fstream.h>
#include <string>

by something newer like

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

 

[void]

Uzytkownik Tim Baker napisal, On 2004-04-29 15:41:

Hi,
I'm trying to master the basics of file operations, but am coming up with a
problem.
The code below should request a file to open, then report whether it was
successful in opening or not. When I try to compile it it seems that the
ifstream fuction is being passed a pointer to the string rather than the
string itself. I tried putting &s and *s ion various places, but to no
avail. Can someone tell me what I'm doing wrong?

thanks,
Tim

******* Testfile.cpp*******


#include <stdio.h>
#include <iostream.h>
#include <fstream.h>
#include <string>

int main(int nNumArgs, char* pzArgs[])
{
string filename;
cout << "What file do you want to open?\n";
cin >> filename;

ifstream inputFile(filename, ios::nocreate);

RTFM!!!
http://www.cppreference.com/
http://www.cplusplus.com/ref/#libs

filename.c_str()
Best
Darek

 

[John Harrison]

Hi,
I'm trying to master the basics of file operations, but am coming up with a
problem.
The code below should request a file to open, then report whether it was
successful in opening or not. When I try to compile it it seems that the
ifstream fuction is being passed a pointer to the string rather than the
string itself. I tried putting &s and *s ion various places, but to no
avail. Can someone tell me what I'm doing wrong?

thanks,
Tim

******* Testfile.cpp*******


#include <stdio.h>

You aren't using the above header file.

#include <iostream.h>
#include <fstream.h>

Both these includes are incorrect, use this

#include <iostream>

#include <string>

Add this

using namespace std;

(see below for explanation)

int main(int nNumArgs, char* pzArgs[])
{
string filename;
cout << "What file do you want to open?\n";
cin >> filename;

ifstream inputFile(filename, ios::nocreate);

ifstream takes a const char*, ios::nocreate is unnecessary and non-standard.

ifstream inputFile(filename.c_str());

if (inputFile.bad())

if (!inputFile.is_open())

{
cout << "Couldn't find that file\n"
<< "Please check the filename and try again\n";
}

else
{
cout << "hooray, you opened " << filename << " like a pro\n";
}
inputFile.close();

Its no necessary to close the file, the destructor will take care of that
for you.

}

Either you are learning from an out of date book, or you are using an out of
date compiler (or both). Its good to get into the habit of using modern
standard C++ if your compiler will accept it. Don't use nocreate, remember
no .h on C++ includes, and standard library names live in the std namespace,
hence 'using namespace std;'

john

 

[Tim Baker]

Either you are learning from an out of date book, or you are using an out
of

date compiler (or both). Its good to get into the habit of using modern
standard C++ if your compiler will accept it. Don't use nocreate, remember
no .h on C++ includes, and standard library names live in the std namespace,
hence 'using namespace std;'

john

Thanks for the helpful replies guys, I guess it's time for me to buy a new
book!

Tim

 

[Sumit Rajan]

out

Thanks for the helpful replies guys, I guess it's time for me to buy a new
book!

Just curious: Which one are you currently using?

 

[Tim Baker]

Just curious: Which one are you currently using?

c++ for dummies :-D
I would have bought a proper book, but this was £2.50 second hand!

 

[Sumit Rajan]

c++ for dummies :-D
I would have bought a proper book, but this was £2.50 second hand!

Try "Thinking in C++" by Bruce Eckel. You can download it (free) from the
author's website:
http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html

Regards,
Sumit.

 

[Tim Baker]

Try "Thinking in C++" by Bruce Eckel. You can download it (free) from the

author's website:
http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html

Regards,
Sumit.

This looks really useful - thanks a lot

Tim