replace some value in text line in c++ - c++

Question

Hi guys i use this code to find the line included seta r_fullscreen "0" and if the value for this line is 0 return MessageBox but my question is if the value of seta r_fullscreenis "0" so how i can replace this value to "1" in this line ?
ifstream cfgm2("players\\config_m2.cfg",ios::in);
string cfgLine;
Process32First(proc_Snap , &pe32);
do{
while (getline(cfgm2,cfgLine)) {
if (string::npos != cfgLine.find("seta r_fullscreen")){
if (cfgLine.at(19) == '0'){
MessageBox(NULL,"run in full Screen mod.","ERROR", MB_OK | MB_ICONERROR);
...

Answer 1

You can use std::string::find() and std::string::replace() to do this. After you have located the line containing the configuration specifier seta r_fullscreen you can do something like the following.
std::string::size_type pos = cfgLine.find("\"0\"");
if(pos != std::string::npos)
{
cfgLine.replace(pos, 3, "\"1\"");
}
You should not assume that the configuration value "0" is at a specific offset as there may be additional spaces between r_fullscreen and "0".
After seeing your additional comments you need to update the configuration file after the changes have been made. The changes you make to the string only apply to the copy in memory and are not automatically saved to the file. You will need to save each line after it has been loaded and changed and then save the updates out to the file. You should also move the process of updating the config file outside of do/while loop. If yo don't you will read/update the file for each process you check.
The example below should get you started.
#include <fstream>
#include <string>
#include <vector>
std::ifstream cfgm2("players\\config_m2.cfg", std::ios::in);
if(cfgm2.is_open())
{
std::string cfgLine;
bool changed = false;
std::vector<std::string> cfgContents;
while (std::getline(cfgm2,cfgLine))
{
// Check if this is a line that can be changed
if (std::string::npos != cfgLine.find("seta r_fullscreen"))
{
// Find the value we want to change
std::string::size_type pos = cfgLine.find("\"0\"");
if(pos != std::string::npos)
{
// We found it, not let's change it and set a flag indicating the
// configuration needs to be saved back out.
cfgLine.replace(pos, 3, "\"1\"");
changed = true;
}
}
// Save the line for later.
cfgContents.push_back(cfgLine);
}
cfgm2.close();
if(changed == true)
{
// In the real world this would be saved to a temporary and the
// original replaced once saving has successfully completed. That
// step is omitted for simplicity of example.
std::ofstream outCfg("players\\config_m2.cfg", std::ios::out);
if(outCfg.is_open())
{
// iterate through every line we have saved in the vector and save it
for(auto it = cfgContents.begin();
it != cfgContents.end();
++it)
{
outCfg << *it << std::endl;
}
}
}
}
// Rest of your code
Process32First(proc_Snap , &pe32);
do {
// some loop doing something I don't even want to know about
} while ( /*...*/ );