How can I copy a file from one directory to another in c/c++

Question

I am looking for a simple example on how to copy a file from one directory to another in C. The program should only use cross platform functions that are native to C.

Answer 1

I made some changes to @te7 answer to copy just one file from one folder to another on MAC. I tried to modify his code to just copy one file but it was partially writing file to destination. So I use different code for file read/write

void copyFile(string srcDirPath, string destDirPath, string fileName)
{


string command = "mkdir -p " + destDirPath;
cerr << endl << "Command = " <<  command.c_str() << endl << endl;
system(command.c_str());


DIR* pnWriteDir = NULL;    /*DIR Pointer to open Dir*/
pnWriteDir = opendir(destDirPath.c_str());

if (!pnWriteDir)
    cerr << endl << "ERROR! Write Directory can not be open" << endl;

DIR* pnReadDir = NULL;    /*DIR Pointer to open Dir*/
pnReadDir = opendir(srcDirPath.c_str());

if (!pnReadDir || !pnWriteDir)
    cerr << endl <<"ERROR! Read or Write Directory can not be open" << endl << endl;

else
{
    string srcFilePath = srcDirPath + fileName;
    const char * strSrcFileName = srcFilePath.c_str();
    fstream in, out;
    in.open(strSrcFileName, fstream::in|fstream::binary);

    if (in.is_open()) {
        cerr << endl << "Now reading file " << strSrcFileName << endl;

        string destFilePath = destDirPath + fileName;
        const char * strDestFileName = destFilePath.c_str();
        out.open(strDestFileName, fstream::out);

        char tmp;
        while(in.read(&tmp, 1))
        {
            out.write(&tmp, 1);
        }
        out.close();
        in.close();
    }
    else
        cerr << endl << "ERROR! File Could not be open for reading" << endl;
}
closedir(pnReadDir);
closedir(pnWriteDir);
}