Writing a backspace in a file

问题

int main(){
std::cout << "Insert file name / or path. \n NOTE: ONLY INPUTS. DELETES PREVIOUS DATA.\nV.6" << std::endl;
std::string filen;
std::cin >> filen;
std::ofstream myFile;
try{
myFile.open(filen, std::ios::out);
}
catch(std::fstream::failure){
std::cout << "Could not open file!\n Make sure the name and data type are valid.";
system("pause");
}
while(true){
    int press = getch();
    if(press == 43) myFile.close();
    if(press == 8){myFile << "\b" << " " << "\b";std::cout << "\b" << " " << "\b" << std::flush;}
    if(press == 13){ myFile << "\n"; std::cout << "\n" << std::flush;}
    if(press != 43 && press != 127 && press != 13 && press != 8){myFile << (char)press;std::cout << (char)press;}
       }
return 0;
}

Whenever I choose a text file and I press backspace, and I check the document and when I check the text document, I get random characters like so:

回答1:

As @BoundaryImposition pointed out already, writing "\b" to your file, will actually write a binary backspace character to your file. What you probably want instead is myFile.seekp(-1, std::ios_base::cur);. If you are on win/dos machine you likely need extra care with '\n' characters because they are translated into 0x0d 0x0a when written to a text stream (thus they require to seek back 2 positions instead of 1).

But generally, if you are not dealing with very huge files, it will be way easier to just store the content in a std::string (using pop_back or erase, to remove characters if needed) and write it to the file when you are finished.

回答2:

Those are not "random characters"; those are backspace characters! i.e. exactly the input you gave.

This can be verified with a hex editor (or piping the output of your program through hexdump et al).

If you wish to replicate the behaviour of common shells, you'll have to write your own code to identify the backspace character and, instead of appending it to myFile, instead eliminate the previously-entered character.

来源：https://stackoverflow.com/questions/43299376/writing-a-backspace-in-a-file

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c++

c++11

fstream