how can i edit the content of a file??

[l3st3r]

Hi guys, im new at c++ and I wonder how to edit the content of a file
here is my "text.txt" inputs

Mark
1000
Lester
200

how can i make it become

Mark
500
Lester
200

[DesiredNote]

http://cplusplus.com/reference/iostream/ifstream/
http://cplusplus.com/reference/iostream/ofstream/

Would you like me to write the program for you?

[l3st3r]

Yes please >.<

[DesiredNote]

#include <iostream>
#include <fstream>

int main(void) {
	std::ofstream writeFile(arg[1]);
	writeFile << "Mark\n500\nLester\n200";
	writeFile.close();
	return 0;
}

Do you want the code to JUST modify the second line or re-write the whole file?

[l3st3r]

I just need to edit the 2nd line. Can you also use using namespace std; Im having problem without it.

[DesiredNote]

What's the problem? There are quite a few reasons why you shouldn't use the whole namespace.

[l3st3r]

i just dont get the std:: >.< having trouble but i can still figure it out.
and also the program is like for a save game file

[DesiredNote]

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

int main(int argc, char *arg[]) {
    std::string buf;
    std::ifstream readFile(arg[1]);
    getline(readFile, buf, '\0');
    readFile.close();
    size_t pos = buf.find_first_of('\n', 2);
    buf.replace(buf.begin()+(pos+1), buf.begin()+(pos+5), "500");
    std::ofstream writeFile(arg[1]);
    writeFile << buf;
    writeFile.close();
    return 0;
}

Just remove every instance of the std prefix and add using namespace std.

[l3st3r]

int main(int argc, char *arg[]) first time encounter.. what do it do??

[Peter87]

@l3st3r
It makes it possible to send arguments to the program through the command line. argc is the number of arguments. arg is an array containing the argc arguments stored as c strings. If argc > 0 then arg[0] will contain the name that was used to invoke the program.

Example:
If you run a program named g++ from the command line as g++ -o k main.cpp then argc and arg will contain the values:
argc = 4
arg[0] = "g++"
arg[1] = "-o"
arg[2] = "k"
arg[3] = "main.cpp"