How can i limit the character to be input in urname and surname?

Question

Zsmash 0 Newbie Poster

13 Years Ago

#include <windows.h>
#include <stdio.h>
#include <conio.h>

void gotoxy(int x,int y);

int main(int argc, char *argv[])


    {


    char urname[1],surname[1],fullname[1];

    start:

    system("COLOR 1c");

    gotoxy(11,9);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,10);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,11);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");   

    gotoxy(11,12);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,13);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");   

    gotoxy(11,14);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,15);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");   



    gotoxy(14,10);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),121);
    printf(" Please enter your name:      ");
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),151);
    printf("                         ");





    gotoxy(14,12);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),121);
    printf(" Please enter your surname:   ");
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),151);
    printf("                         ");


    gotoxy(14,14);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),121);
    printf(" Your name is:                ");
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),151);
    printf("                         ");



    gotoxy(45,10);
    gets(urname);


    gotoxy(45,12);
    gets(surname);

    gotoxy(45,14);
    printf("%s %s",urname,surname);
    gets(fullname);
{    
     char choice;

   gotoxy(35,11);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
    printf(" Do you want to enter  ");
   gotoxy(35,12);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
    printf(" another entry?        ");
   gotoxy(35,13);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
    printf(" YES                  ");
   gotoxy(40,13);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
    printf("          NO      ");
    choice= getche();
   if (choice=='y'){
   goto start;
}
   else
   printf("BYE");
}





}


void gotoxy(int x, int y){
     COORD coord = {x,y};
     SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE),coord);


     }

c c++

Edited 13 Years Ago by JorgeM because: move to C forum

3 Contributors
5 Replies
395 Views
1 Day Discussion Span
Latest Post 13 Years Ago Latest Post by Ancient Dragon

Dani AI

Generated 9 Months Ago

Quick diagnosis and the immediate fixes you need

The core problems in ’s original code are (1) declaring name buffers as char x[1] (no room for characters plus the terminating '\0'), and (2) using gets() which performs no bounds checking. gets() is explicitly unsafe and was removed from the C standard (do not use it). (en.cppreference.com)

Practical, safer approaches

Allocate a buffer large enough for the longest expected input plus one byte for the NUL terminator, or use a dynamic reader that grows the buffer for you. On POSIX systems consider getline() which will allocate/resize a buffer automatically; on other systems pick a sensible maximum and enforce it. (man7.org)
Prefer fgets() (reads at most N-1 chars and leaves a trailing newline which you should strip) or the C11/Microsoft safer alternative gets_s() where available. Always check the function return value before using the buffer. (en.cppreference.com)

Notes about the thread answers

was correct pointing out the tiny arrays and the need for fgets/stdio.h. That is the simplest immediate fix. (en.cppreference.com)
’s gets_ex approach (reading keystrokes with getch) is a workable way to limit visible input, but it omits proper editing support (backspace, arrow keys), and it does not handle Unicode or redirected stdin. If you need richer console editing or Unicode on Windows, use the console APIs such as ReadConsole/ReadConsoleW instead. (learn.microsoft.com)

Quick checklist before shipping

Stop using gets(); allocate or obtain a properly sized buffer; read with fgets, getline, or a secure alternative; strip the trailing newline; validate character content and length; and check return values. If you implement raw key-by-key input, explicitly handle backspace and control characters and document that behavior. (en.cppreference.com)

These changes will make the program safe against buffer overruns and behave predictably for users typing and editing their names.

All 5 Replies

Ancient Dragon 5,243 Achieved Level 70

13 Years Ago

char urname[1],surname[1],fullname[1];

How many people do you know who have a first, middle and last name that consists of only 1 character??? gets() doesn't allocate new memory, you have to do that yourself. You sort of have to guess about how big to make those variables then use fgets(), not gets(), to limit user input like this:

fgets(urname, sizeof(urname), stdin);

Ancient Dragon 5,243 Achieved Level 70

13 Years Ago

fgets() is declared in stdio.h not stdlib.h. Your program doesn't need wincon.h because it isn't using anything from that file.

Edited 13 Years Ago by Ancient Dragon

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thanhvy 0 Newbie Poster · Answer 1 · 2013-09-04T17:59:33+00:00

You can't limit characters by using gets
I create simple function to limits input string

#include <Windows.h>
#include <WinCon.h>
#include <conio.h>
#include <stdlib.h>

void gotoxy(int x,int y);
void gets_ex(char*, int max_chars);

int main(int argc, char *argv[])
{
    char urname[10], surname[10], fullname[20];

start:

    system("COLOR 1c");

    gotoxy(11,9);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,10);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,11);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");   

    gotoxy(11,12);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,13);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");   

    gotoxy(11,14);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");

    gotoxy(11,15);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),291);
    printf("                                                             ");   

    gotoxy(14,10);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),121);
    printf(" Please enter your name:      ");
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),151);
    printf("                         ");

    gotoxy(14,12);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),121);
    printf(" Please enter your surname:   ");
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),151);
    printf("                         ");


    gotoxy(14,14);
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),121);
    printf(" Your name is:                ");
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),151);
    printf("                         ");

    gotoxy(45, 10);
    // gets(urname);
    // fgets(urname, 10, stdin);
    gets_ex(urname, 10);

    gotoxy(45, 12);
    //gets(surname);
    gets_ex(surname, 10);

    gotoxy(45, 14);
    printf("%s %s",urname,surname);
    //gets(fullname);
    gets_ex(fullname, 20);

    {    
        char choice;

        gotoxy(35,11);
        SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
        printf(" Do you want to enter  ");
        gotoxy(35,12);
        SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
        printf(" another entry?        ");
        gotoxy(35,13);
        SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
        printf(" YES                  ");
        gotoxy(40,13);
        SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),11);
        printf("          NO      ");
        choice= getche();
        if (choice=='y')
        {
            goto start;
        }
        else
            printf("BYE");
    }
}

void gotoxy(int x, int y)
{
    COORD coord = {x,y};
    SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE),coord);
}

void gets_ex(char* pszOut, int max_chars)
{
    int ch;
    int nchar = 0;
    memset(pszOut, '\0', max_chars);

    do
    {
        ch = getch();

        if(ch != VK_RETURN && nchar < max_chars - 1)
        {
            putch(ch);
            pszOut[nchar] = ch;
            nchar++;
        }
    }
    while(ch != VK_RETURN);
}

Zsmash 0 Newbie Poster · Answer 2 · 2013-09-05T04:19:27+00:00

Zsmash 0 Newbie Poster

13 Years Ago

thank you sir... it works :)

Zsmash 0 Newbie Poster · Answer 3 · 2013-09-05T04:29:41+00:00

even if there's no

#include<WinCon.h>
#include<stdlib.h>

>

How can i limit the character to be input in urname and surname?

Dani AI

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