Multiple number entry with a keypad?

Using Arduino Programming Questions
19

Again, I don't have a keypad, but see if this works:

#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 3; //three columns
char keys[ROWS][COLS] = {
  {'1', '2', '3'},
  {'4', '5', '6'},
  {'7', '8', '9'},
  {'*', '0', '#'}
};
byte rowPins[ROWS] = {8, 7, 6, 5}; //connect to the row pinouts of the kpd
byte colPins[COLS] = {4, 3, 2}; //connect to the column pinouts of the kpd

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup() {
  Serial.begin(9600);
}

void loop() {
  char entryStr[12];
  char key;
  int i = 0;

  while (1) {
    key = keypad.getKey();
    switch (key) {
      case '*':                     // Cancel
        Serial.println("");
        Serial.println("Canceled");
        break;
      case '#':                     // Done
        entryStr[i] = '\0';
        strcat(entstr, ".mp3");
        Serial.print(entstr);
        break;
      default:                      // Add a char
        entryStr[i++] = key;
        break;
    }
    if (key == '#' || key == '*') { // Start over??
      break;
    }
  }
}

Note the disappearance of memset() and filename and fewer statements on key and i.