Block Control Characters

This is a discussion on Block Control Characters within the C++ Programming forums, part of the General Programming Boards category; I'm making a payroll application which takes input from cin, it validates the data (has a while loop in it). ...

  1. #1
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    Block Control Characters

    I'm making a payroll application which takes input from cin, it validates the data (has a while loop in it). The problem is if I 'accidently' press Ctrl+Z it just keeps looping the prompt on the screen as I am locked out of the program. what canI do to block these special characters Ctr+Z and Ctrl+C and if there are others?

  2. #2
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    ctrl+z and ctrl+c are "EOF" some where in your program you are telling it to ignor them. In your test condition add a test for EOF to break your
    loop.

  3. #3
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    how can i do that? the code im delaying with is :
    Code:
    do {
          cout << "Enter data: ";
          cin >> data}
    while (!validData);
    }

  4. #4
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    Code:
    cout << "Enter data: ";
    while(cin >> data) {
       if(valid) {
       } else break;
        cout << "Enter data: ";
    }

  5. #5
    ... arjunajay's Avatar
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    in 'ctype' header, there are functions like 'isalnum()', 'isdigit', etc which you can use to check for valid input or create one your self using the ascii chart...

  6. #6
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    we are suppose to use a do while loop because we are only suppose to prompt once! Our lecturer said prompting for the samething more than once was 'inefficient', so I can't use
    Code:
    cout << "Enter data: ";
    while(cin >> data) {
    if(valid) {
    } else break;
    cout << "Enter data: ";
    }
    would that even stop the control characters? i don't quite see how...
    Last edited by Hexxx; 02-11-2006 at 08:33 PM.

  7. #7
    and the hat of wrongness Salem's Avatar
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    ctrl-z is the end of file marker for terminal input
    ctrl-c is the interrupt signal, which kills your program unless you handle or ignore it
    Code:
    #include <iostream>
    #include <string>
    #include <signal.h>
    using namespace std;
    
    volatile bool sigCaught = false;
    // http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_CRT_signal.asp
    void catcher ( int signal ) {
      sigCaught = true;
    }
    
    int main ( ) {
      bool  done = false;
      /* catch ctrl-C, test sigCaught below if you want to know about it */
      // signal ( SIGINT, catcher );
      /* ignore ctrl-C */
      signal ( SIGINT, SIG_IGN );
    
      while ( !done ) {
        char input[100];
        while ( !done &&
                cin.getline(input,sizeof input) ) {
          string sInput = input;
          cout << sInput << endl;
          if ( sInput == "exit" ) {
            done = true;
          }
        }
        if ( cin.eof() ) {
          cin.clear();
          cout << "EOF detected, ignored" << endl;
        }
      }
    
      return 0;
    }

  8. #8
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    ok i figured out the cin.eof by myself. thanks a lot for the signal part!

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