function problem in password generator

hi guys,
i've written a password generator and would like to make a function of it (for future use), but when i use the function i get into an unending loop, here's the code:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void generate_password(int);

int main(void)
{
    int password_length;
    printf("\nThis is a password generator.");
    printf("\nEnter the length of the password: ");
    scanf("%d",password_length);
    printf("\nThe generated password is: ");
   
    generate_password(password_length);
    return 0;
}

void generate_password(length)
{
    int length;
    srand(time(NULL));   
    while (length>0)
    {
       
        int cha;
        cha=rand()%128;
        if((cha>=48 && cha<=57) || (cha>=65 && cha<=90) || (cha>=97 && cha<=122))
        {
          printf("%c",cha);
          length--;
        }
    }
}

---

problem: when the above code is executed (after compling of course), it gets in a unending loop...

BUT, with the next code the program works fine:

Code:

---

#include <stdio.h>
#include <stdlib.h> 
#include <time.h> 

int main(void)
{
  srand(time(NULL));
  int cha;
  int length;
  printf("This is a password generator.");
  printf("\nEnter the length of your password: ");
  scanf("%d",&length);
  printf("\nYour generated password is: ");
  while (length>0)
  {
    cha=rand()%128;
    if((cha>=48 && cha<=57) || (cha>=65 && cha<=90) || (cha>=97 && cha<=122))
    {
        printf("%c",cha);
        length--;
    }
  }
  char ch;
  printf ("\nPress any key to continue");
  ch=getch();
  return 0;
}

---

what did i do wrong by changing the above code to a function?

I’m no C expert, but shouldn’t the top line of the function be:

Code:

---

void generate_password(int length)

---

And without

Code:

---

int length;

---

My guess is that length is somehow being set to some unholy huge number. I’m messing with it and I’ll let you know what I find.

i'll give it a try, and thanks for the help.....

[edit]
gee, i feel stupid! i just made a very stupid mistake:

Code:

---

scanf("%d",password_length);

---

should be :

Code:

---

scanf("%d",&password_length):

---

well, thanks for the reply anyway :)[/edit]

Ok, the following works for me in GCC under Cygwin and also in Dev-C++:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void generate_password(int);

int main(void)
{
   
    int password_length;
    printf("\nThis is a password generator.");
    printf("\nEnter the length of the password: ");
    scanf("%d",&password_length);
    printf("\nThe generated password is: ");
 
    generate_password(password_length);
    return 0;
}

void generate_password(int length)
{
    srand(time(NULL));
 
    while (length>0)
    {
       
        int cha;
        cha=rand()%128;
        if((cha>=48 && cha<=57) || (cha>=65 && cha<=90) || (cha>=97 && cha<=122))
        {
          printf("%c",cha);
          length--;
        }
    }
}

---

Enjoy

edit: notice the pass by address in the scanf statement

hahaha, you figured it out at about the same time as i did, but thanks for your help anyways :)

those stupid "&", they catch me out all the time and its the first thing i look for now,

i2c

i know what you mean :D

very nice but these does not support different finds of passwords!!

like :

digits only
letters only
capitalized letters only
special characters

of a combination of all !!

very nice website lepricaun

i found some cool stuff there

check mine >>

It does i you modify it. Now stop bringing up old threads unless you have something useful to add (like the code to do what you want).

Just thought I'd suggest the following:

Code:

---

By lepricaun

void generate_password(length)
{
    int length;
    srand(time(NULL));   
    while (length>0)
    {
       
        int cha;
        cha=rand()%128;
        if((cha>=48 && cha<=57) || (cha>=65 && cha<=90) || (cha>=97 && cha<=122))
        {
          printf("%c",cha);
          length--;
        }
    }
}

---

Yes this works, however, should you be declaring the cha variable every time you loop round in the while loop? It's not efficient. 9/10 from me, especially as you didn't do that in the code this superceeded! LOL

yes, your right, but sorry mate, you're a little behind...

this is an old thread, and old code too ;)

here's the final version of the password generator:
pwgenCL_2

Code:

---

/*
pwgenCL version 2 (pwgenCL_2)Copyright (C) 2004 Scorpius, password generator,
written as a command line scripting utility.
this program is freesource, which means you may use and/or modify it under the GPL license.
if you'd like to contact me with comments/bugs/suggestions or just to say hello,
my email address is: [email protected].
 
i hope you enjoy using my program and that you find it usefull :)       
 
to compile it under windows, get a copy of Dev-C++ (it's free), or another C/C++ compiler.
to compile it under linux, just type "gcc -o pwgenCL_2 pwgenCL_2.c" (without the " quotes)
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <strings.h>

char *generated_password(char*, int,int);

int main(int argc, char** argv)
{  /*the character sets*/
    char *very_easy_set = "abcdefghijklmnopqrstuvwxyz";
    char *very_easy2_set = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    char *easy_set = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    char *medium_set = "abcdefghijklmnopqrstuvwxyz0123456789";
    char *hard_set = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    char *hard2_set = "\\][^_abcdefghijklmnopqrstuvwxyz0123456789";
    char *very_hard_set = "!\"#$%'(*)+,-./abcdefghijklmnopqrstuvwxyz0123456789";
    char *extreme_set = "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
   
    int characterset=0;
    int password_length=0;
    int user_supplied=0;
    if(argc!=4)
    {
            printf("\npwgenCL_2,commandline password generator, Copyright (C) 2004 Scorpius");
            printf("\n\npwgenCL_2 is free software; you can redistribute it and/or modify");
            printf("\nit under the terms of the GNU General Public License as published by");
            printf("\nthe Free Software Foundation; either version 2 of the License.");
            printf("\n\npwgenCL_2 is distributed in the hope that it will be useful,");
            printf("\nbut WITHOUT ANY WARRANTY; without even the implied warranty of");
            printf("\nMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the");
            printf("\nGNU General Public License for more details.");
            printf("\n\nYou should have received a copy of the GNU General Public License");
            printf("\nalong with this program; if not, write to the Free Software");
            printf("\nFoundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA\n");
            printf("\n\t  ***Contact Scorpius: [email protected]***");
            printf("\n\nCharacter sets:");
            printf("\n1: (a-z)\t\t\t\t\tvery easy password");
        printf("\n2: (A-Z)\t\t\t\t\tvery easy password");
        printf("\n3: (a-z,A-Z)\t\t\t\t\teasy password");
        printf("\n4: (a-z,0-9)\t\t\t\t\tmedium password");
        printf("\n5: (A-Z,a-z,0-9)\t\t\t\thard password");
        printf("\n6: (a-z,0-9, \\ ] [ ^ _ )\t\t\thard password");
        printf("\n7: ( ! \" # $ % ' ( * ) + , - . /  ,a-z,0-9)\tvery hard password");
        printf("\n8: full keyboard characters (except space), almost impossible to crack\n\n");
        printf("The maximum password length is 256 characters\n");
        printf("Usage: %s <characterset> <password length> <user supplied number>\n",argv[0]);
        printf("\n*The <user supplied number> is inserted to create extra randomness*\n");
        printf("\nExample: %s 8 15 5454303\n",argv[0]);
        return 0;
    }
    if(argc==4)/*if all parameters, (characterset,passwordlength,randomization number) run the program*/
    {
            characterset=atoi(argv[1]);/*create integer from the argument*/
            password_length=atoi(argv[2]);/*create integer from the argument*/
            user_supplied=atoi(argv[3]);/*create integer from the argument*/
            if (password_length<1)
        {
                printf("Password length: %d is too small.\n",password_length);
                return EXIT_FAILURE;
                }
                if (password_length>256)
                {
                printf("Password length: %d is too large.\n",password_length);
                return EXIT_FAILURE;
                }
            switch(characterset)
            {
                case 1:
                        generated_password(very_easy_set,password_length,user_supplied);
                        break;
                case 2:
                        generated_password(very_easy2_set,password_length,user_supplied);
                        break;
                case 3:
                        generated_password(easy_set,password_length,user_supplied);
                        break;
                case 4:
                        generated_password(medium_set,password_length,user_supplied);
                        break;
                case 5:
                        generated_password(hard_set,password_length,user_supplied);
                        break;
                case 6:
                        generated_password(hard2_set,password_length,user_supplied);
                        break;
                case 7:
                        generated_password(very_hard_set,password_length,user_supplied);
                        break;
                case 8:
                        generated_password(extreme_set,password_length,user_supplied);
                        break;
              default:
                        printf("Invalid character set\n");
                                    return EXIT_FAILURE;
                        break;
            }
            return EXIT_SUCCESS;
    } 
    else return EXIT_FAILURE; 
}

/*the password generator function*/

char *generated_password(char* char_set, int length,int user_number)
{
       
        srand(user_number*time(NULL));
        int loop;
        int set_length=strlen(char_set);
   
        for(loop=0;loop<length;loop++)
        {
            putchar(char_set[rand()%set_length]);
        }
        printf("\n");
}

---

and as you can see, the declaration of the variable isn't done in the loop anymore :p

for more info on this program check this thread.