Read and write the same file

[YUS]

First of all, I'm a c++ beginner.. as u will see..

I'd like to do this:

- The code open a file
- it searchs for the string "BUDGET = "
- the budget value is overwritten or at least the entire row.

CODE:

fstream file;
memset(buf,0,512);
file.open(nomefile, ios:ut | ios::in);
do{ file.getline(buf, 512, '\n');
} while(!strncmp(buf, "BUDGET", 6));

file << "BUDGET = " << budget << endl;

The problem is that the file is not written, no changes are made to the
file.
I've also tried with ios::app but with no results.

How I can do ?
Thanks to all.

 

[Jon Rea]

First of all, I'm a c++ beginner.. as u will see..

I'd like to do this:

- The code open a file
- it searchs for the string "BUDGET = "
- the budget value is overwritten or at least the entire row.

CODE:

fstream file;
memset(buf,0,512);
file.open(nomefile, ios:ut | ios::in);
do{ file.getline(buf, 512, '\n');
} while(!strncmp(buf, "BUDGET", 6));

file << "BUDGET = " << budget << endl;

The problem is that the file is not written, no changes are made to the
file.
I've also tried with ios::app but with no results.

How I can do ?
Thanks to all.

You need to close the filestream to write the current memory to the file...

Jon Rea

 

[TB]

YUS sade:

First of all, I'm a c++ beginner.. as u will see..

I'd like to do this:

- The code open a file
- it searchs for the string "BUDGET = "
- the budget value is overwritten or at least the entire row.

CODE:

fstream file;
memset(buf,0,512);
file.open(nomefile, ios:ut | ios::in);
do{ file.getline(buf, 512, '\n');
} while(!strncmp(buf, "BUDGET", 6));

file << "BUDGET = " << budget << endl;

The problem is that the file is not written, no changes are made to the
file.
I've also tried with ios::app but with no results.

How I can do ?
Thanks to all.

I believe, IIRC, that you after a read must do
a seekp() before you write, and vise versa (but with
seekg()).