CODEWITHSUNDEEP
c++file
Martin Vegter
Martin Vegter

Reputation: 527

overwrite file (not append) in c++

I need to modify code written in c++. The code opens a file authfile and writes 49 bytes to it. In case the file already exists, I need to make sure the existing data will be overwritten.

The original code first deleted the file and then created a new file. For reasons beyond this discussion, I cannot delete the file, I only need to make sure it is empty, before i write new data to it.

Below is the function that writes the data. How can I modify it, so thatexisting content of the file will be overwritten ?

I suppose, I need to tchange the options of popen

bool Util::add_mcookie(const std::string &mcookie, const char *display,
    const std::string &xauth_cmd, const std::string &authfile)
{
        FILE *fp;
        std::string cmd = xauth_cmd + " -f " + authfile + " -q";

        fp = popen(cmd.c_str(), "w");
        if (!fp)
                return false;
        fprintf(fp, "remove %s\n", display);
        fprintf(fp, "add %s %s %s\n", display, ".", mcookie.c_str());
        fprintf(fp, "exit\n");

        pclose(fp);
        return true;
}

Upvotes: 0

Views: 297

Answers (1)

SelfTaught
SelfTaught

Reputation: 499

Change popen to fopen and pclose to fclose. popen / pclose is for opening / closing a process. Also, it looks like you're creating the process with flags. You just need to give fopen the file path

Upvotes: 3

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