Question

I have problem with remove() function

First, look at the example and you will see the problem

cout << "Please enter the phone number to remove" << endl << "Phone number: ";
string rphNumber;
cin >> rphNumber;
ifstream ifile("db/" + rphNumber + ".txt");
if(ifile)
  remove(("db/" + rphNumber + ".txt").c_str()); // the problem here
else
  cout << "failure" << endl;

The problem in this line (the file path), always the function return -1 Although the file exists

remove(("db/" + rphNumber + ".txt").c_str());

Answer 1

Your problem may be that you still have ifile open at the point where you try to remove it. Some operating systems don’t let you delete a file that’s open. Another possibility is that the string rphNumber might have a newline at the end which you need to strip off before assembling the filename. (I don’t remember if cin does that or not.)

Your problem definitely is that you are trying to find out if a filesystem operation will work. You can’t do that. In between when you make the test and when you actually try to do the operation, another process may change things so that the operation won’t work, even though your test said it will. Also, being able to open a file is not the same as being able to delete a file; there are probably lots of files on your hard drive that you can open but not delete (such as /dev/null).

You have to just do the filesystem operation. It will tell you if it worked or not, with its return value. Then, when it doesn’t work, you look at errno to find out why. The C utility function strerror (include <cstring>) will convert an errno value to a human-readable error message.

Putting it together, here’s the correct way to write your program:

cout << "Please enter the phone number to remove.\nPhone number: ";
string rphNumber;
cin >> rphNumber;
string fname("db/" + rphNumber + ".txt");

if (remove(fname.c_str()))
    cout << "Failed to delete '" << fname << "': " << strerror(errno) << '\n';
else
    cout << '\'' << fname << "' successfully deleted.\n";

Incidentally, never use endl; if '\n' doesn’t work, it means your streambufs are not configured correctly.