Thread: Help in checking password in a file

Originally Posted by Lokesh

i think you should use the
strcmp function which returns 0(zero) if the two strings are same
syntax:

Code:

x=strcmp(user,fuser);
if(x==0)
{
y=strcmp(pass,fpass);
if(y==0)
{
printf("authrised user");
}
}

this will surely work
i have used it before.....

what should i declare x and y and i??

Originally Posted by frodonet

The loop is reading the data from the file....but i don think it's looping cause i have entered the user id and password before the loop...

so then the loop can check one time for the user ...

i think i understand, if i press wrong username...it thus shows username not found...

but when i press correct password...it still close the program

The logic is like this:
Read one line from file, store in line_buffer.
Condition for loop is if the read succeeds. In other words, if the read fails, the loop breaks.
Then you break the data into separate variables.
You check the user and fuser strings to see if they're equal. If yes, then you check if the pass and fpass is equal. If yes, then print a message and wait for a keypress.
Then continue the loop, since you haven't entered any break or return.
Loop.

Originally Posted by Lokesh

i think you should use the
strcmp function which returns 0(zero) if the two strings are same
syntax:

Code:

x=strcmp(user,fuser);
if(x==0)
{
y=strcmp(pass,fpass);
if(y==0)
{
printf("authrised user");
}
}

this will surely work
i have used it before.....

Originally Posted by frodonet

what should i declare x and y and i??

That's the code I've already presented to you. No need to do it again.

Originally Posted by Elysia

The logic is like this:
Read one line from file, store in line_buffer.
Condition for loop is if the read succeeds. In other words, if the read fails, the loop breaks.
Then you break the data into separate variables.
You check the user and fuser strings to see if they're equal. If yes, then you check if the pass and fpass is equal. If yes, then print a message and wait for a keypress.
Then continue the loop, since you haven't entered any break or return.
Loop.

sorry to made you so mad.

it's just that i'm kind of dumb. please forgive me, i knew i asked so many questions.

so sorry...

Originally Posted by Elysia

Not mad. Just telling you where the problem lies
You should remember that code execution always continues forward unless you tell the compiler it shouldn't. To do that, you can use break (breaks a loop), continue (jumps to the beginning of the loop again) or return (exits the function).
There's also goto, but many consider it bad. Goto jumps to a specific place in your code. Take care when using it, though, since it can really make your code look messy.

i have put breaks...it still the same thing....

Code:

#include<stdio.h>

main( )
 {
     FILE *fpassword;
     char c, line_buffer[100], user[20], pass[5];
     fpassword = fopen("C:\\PASSWD.TXT", "r");
     if (fpassword == NULL) printf("File doesn't exist\n");

     printf("Enter userid: ");
     fgets(user,sizeof(user),stdin);

     printf("Enter password: ");
     fgets(pass,sizeof(pass),stdin);

     while( fgets(line_buffer,sizeof(line_buffer),fpassword) != NULL )  /* read from file while still data available */
     {
            char ftemp[20], fpass[20], fuser[20];
            if( sscanf(line_buffer,"%.20s %.20s %.20s",ftemp,fpass,fuser) != 3 )  /* Make sure we parsed 3 fields from the line */
            {
                 /* Invalid line in file, skip to next one   */
            }
            else /* Otherwise, we got 3 fields */
            {
                  if (strcmp(user, fuser) == 0) /* OK, found the username the user inputted */
                  {
	                 if (strcmp(pass, fpass) == 0) /* Now, check if passwords match, if they do not, user entered a faulty password */
                     {
                     printf("User authorized");
                     getchar();
                     }
                     else
                     {
                     printf("User not authorized");
                     getchar();
                     }
                  }
            }
      }
    fclose(fpassword);

    getchar();
 }

arghhh... the program still closes after i pressed userid and password.

i just couldn't figure it out help me

Originally Posted by Salem

5 chars for a password?
Since one of them will be \0, and the other one will be a \n (for a complete line), that leaves you with 3 chars.
Type any more than that, and you're out of sync in the rest of the program.

i have changed my pass[5] into pass[20]...

Originally Posted by Salem

With fgets(), use an array of BUFSIZ characters, then validate/process that buffer to it's correct variable in your program.

how do i do this??? how to validate??

Originally Posted by matsp

Validate in this case refers to checking the name/password.

--
Mats

checking the name and password inputted or checking name and password with the file?

any examples?? this BUFSIZ is really new to me...

Originally Posted by MacGyver

BUFSIZ is just a constant that is defined to be some value specific to the compiler/system.

so how do i use it to check name and password??

Originally Posted by matsp

Well, in this case, validation could also be considered "validating that the input is correct".

For example, if you use fgets() to get a short string, and someone types a longer string, the next fgets() will get the remaining data from the input buffer.

The input buffer is BUFSIZ long, so we can't get more data than a BUFSIZ at a time [most likely].

--
Mats

i would appreciate an example...a simple one. there's no way a beginner can understand a c code just by sentences.