// Program shows copying one text file from source location  // to any other location (destination), plus possibility of changing its name,  // and also shows many language features in exception handling.  // This program should be run from the command prompt      #include<iostream>  #include<stdio.h>  #include<stdexcept>      using namespace std;      class PathError : public runtime_error  {      public:          PathError(const char *x) : runtime_error(x)      {}  };      // function to open source file for read      FILE* source (char* argvs[])  {      FILE *in;      //open source file for read      if((in = fopen(argvs[1],"r"))==NULL)      {          throw PathError("attempted to open wrong input file path");//terminate function      }      return in;  }      //function to create destination file for writting  FILE* destination (char* argvs[])  {      FILE *out;      //open destination file for write      if((out = fopen(argvs[2],"w")) == NULL)      {          throw PathError("attempted to open wrong output file path");//terminate function      }      return out;  }      int main(int argc, char *argv[])  {      FILE *in, *out;      bool flag = 1;      int temp;      while(argc == 3)      {          try          {              in = source( argv );              out = destination( argv );              argc = 0;          }          catch(PathError& PathError)          {              cerr <<"\nException occured: " << PathError.what() << endl;              return -1;          }              while(!feof(in))//test for it is not end of input file          {              temp = fgetc(in);//get char from (in)file              if( temp != EOF)              {                  fputc(temp,out);//put char to (out) file              }          }          fclose(in);          fclose(out);          cout<<"\n\t 1 file copied.\n";          flag = 0;      }      if( flag != 0 )      {          cerr<<"\nWrong argument list!!!\n\n";          return -1;      }      return 0;  }