String User Input not working | Together C & C++ | Page 1

shy fractal Oct 3, 2022, 6:04 PM

#

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
    char hard_username[10] = "waseem";
    char hard_pass[10] = "waseem123";
    char username[10];
    char password[10];

    for (int i =0; i<4; i++){
        printf("Please Insert Username: \n");
        gets(hard_username);
        printf("Please Insert Password:\n");
        scanf("%s", hard_pass);

        if (hard_username == username && hard_pass == password){
            printf("Perfect Match !\nYou cab Log Successfully!");
            break;
        } else{
            printf("USERNAME OR PASSWORD DON'T MATCH!\n");
        }

    }

stray laurelBOT Oct 3, 2022, 6:04 PM

#

When your question is answered use !solved to mark the question as resolved.

Remember to ask specific questions, provide necessary details, and reduce your question to its simplest form. For more information use !howto ask.

shy fractal Oct 3, 2022, 6:04 PM

#

what's wrong!!

frosty valley Oct 3, 2022, 6:04 PM

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What do you want do do?

shy fractal Oct 3, 2022, 6:05 PM

#

    char hard_username[10] = "waseem";
    char hard_pass[10] = "waseem123";
    char username[10];
    char password[10];

    for (int i =0; i<4; i++){
        printf("Please Insert Username: \n");
        gets(username);
        printf("Please Insert Password:\n");
        scanf("%s", hard_pass);

        if (hard_username == username && hard_pass == password){
            printf("Perfect Match !\nYou cab Log Successfully!");
            break;
        } else{
            printf("USERNAME OR PASSWORD DON'T MATCH!\n");
        }

    }

shy fractal Oct 3, 2022, 6:05 PM

#

frosty valley What do you want do do?

a C program that asks the user to enter a username and password. Your program should check whether both username and password match a hardcoded username and password, and display meaningful messages in case the username or the password is incorrect. The program gives the user three chances to enter the correct values. Note: assume that both the username and the password are numbers.

#

oh number

frosty valley Oct 3, 2022, 6:06 PM

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Then first of all it should be i < 3

shy fractal Oct 3, 2022, 6:06 PM

#

but how to it using strigs

shy fractal Oct 3, 2022, 6:06 PM

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frosty valley Then first of all it should be `i < 3`

ah yes

frosty valley Oct 3, 2022, 6:07 PM

#

Also you can't use ==. You need to use strcmp

#

Also gets is inherently dangerous

#

as is scanf

#

you should use fgets instead

shy fractal Oct 3, 2022, 6:08 PM

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frosty valley Also you can't use `==`. You need to use `strcmp`

oh i c java flashbacks

frosty valley Oct 3, 2022, 6:08 PM

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btw: http://sekrit.de/webdocs/c/beginners-guide-away-from-scanf.html

#

a super worthy article to read

shy fractal Oct 3, 2022, 6:08 PM

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the && is used correctly right?

frosty valley Oct 3, 2022, 6:09 PM

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yes

shy fractal Oct 3, 2022, 6:09 PM

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|| is for OR

frosty valley Oct 3, 2022, 6:09 PM

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yes

shy fractal Oct 3, 2022, 6:09 PM

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wait how to use strcmp()

#

strcmp(hard_username, username);

frosty valley Oct 3, 2022, 6:09 PM

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!man 3 strcmp

nocturne ventureBOT Oct 3, 2022, 6:10 PM

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strcmp(3)

strcmp, strncmp - compare two strings

The strcmp() function compares the two strings s1 and s2. The
locale is not taken into account (for a locale-aware comparison,
see strcoll(3)). The comparison is done using unsigned
characters.

Synopsis


#include <string.h>

int strcmp(const char *s1, const char *s2);
int strncmp(const char *s1, const char *s2, size_t n);

Also See

bcmp(3), memcmp(3), strcasecmp(3), strcoll(3), string(3), strncasecmp(3), strverscmp(3), wcscmp(3), wcsncmp(3), ascii(7)

shy fractal Oct 3, 2022, 6:10 PM

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should I use pointers too?

#

same as example

frosty valley Oct 3, 2022, 6:10 PM

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arrays, when passed to a function, automatically decay to pointers

#

So you're good with just using arrays

rancid thunder Oct 3, 2022, 6:11 PM

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shy fractal ```c char hard_username[10] = "waseem"; char hard_pass[10] = "waseem123"...

both the calls to gets and scanf there have no way of knowing when to stop writing to the buffer, so they may overflow the buffers
did you mean to write to password in your call to scanf? password never gets initialized anywhere

shy fractal Oct 3, 2022, 6:13 PM

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rancid thunder both the calls to `gets` and `scanf` there have no way of knowing when to stop w...

oooh

#

yes

#

   char hard_username[10] = "waseem";
    char hard_pass[10] = "waseem123";
    char username[10];
    char password[10];

    for (int i =0; i<3; i++){
        printf("Please Insert Username: \n");
        gets(username);
        printf("Please Insert Password:\n");
        scanf("%s", password);

        if ( strcmp(hard_username, username) && strcmp(hard_pass, password)){
            printf("Perfect Match !\nYou cab Log Successfully!");
            break;
        } else{
            printf("USERNAME OR PASSWORD DON'T MATCH!\n");
        }

    }

#

still not working
note: I am using gets and scanf for practice purposes

frosty valley Oct 3, 2022, 6:14 PM

#

what's not working

shy fractal Oct 3, 2022, 6:15 PM

#

ooooh i think it's the strcmp I have to fix one sec

#

    char hard_username[10] = "waseem";
    char hard_pass[10] = "waseem123";
    char username[10];
    char password[10];

    for (int i =0; i<3; i++){
        printf("Please Insert Username: \n");
        gets(username);
        printf("Please Insert Password:\n");
        scanf("%s", password);

        if ( strcmp(hard_username, username) ==0 && strcmp(hard_pass, password) == 0){
            printf("Perfect Match !\nYou cab Log Successfully!");
            break;
        } else{
            printf("USERNAME OR PASSWORD DON'T MATCH!\n");
        }

    }

This works for perfect match Thanks

silent bobcat Oct 3, 2022, 6:16 PM

#

shy fractal ```c char hard_username[10] = "waseem"; char hard_pass[10] = "waseem123"...

this should word

#

work

shy fractal Oct 3, 2022, 6:16 PM

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wait wait

frosty valley Oct 3, 2022, 6:16 PM

#

ah yes. strcmp returns 0 if they're equal.

silent bobcat Oct 3, 2022, 6:16 PM

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^

shy fractal Oct 3, 2022, 6:16 PM

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Please Insert Username:
waseem
Please Insert Password:
waseem321
USERNAME OR PASSWORD DON'T MATCH!
Please Insert Username:
Please Insert Password:
waseem
USERNAME OR PASSWORD DON'T MATCH!
Please Insert Username:
Please Insert Password:

why's this happening?!

#

for matching password and username worked now

silent bobcat Oct 3, 2022, 6:18 PM

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shy fractal ```c char hard_username[10] = "waseem"; char hard_pass[10] = "waseem123"...

you would have to replace gets(username) with scanf

shy fractal Oct 3, 2022, 6:20 PM

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works thanks!

#

no idea why tho ?

silent bobcat Oct 3, 2022, 6:20 PM

#

بكرا بشرحلك

shy fractal Oct 3, 2022, 6:20 PM

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rancid thunder both the calls to `gets` and `scanf` there have no way of knowing when to stop w...

I think it's related to the buffer thing

#

char[10] palindrome_checker(char msg[10]){
    return msg;
}

how do we return arrays of character aka strings

#

@frosty valley got an extra minute plz

frosty valley Oct 3, 2022, 6:27 PM

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you can't return arrays from functions

rancid thunder Oct 3, 2022, 6:28 PM

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shy fractal ```c char[10] palindrome_checker(char msg[10]){ return msg; } ``` how do we ...

you need to wrap the array in a structure and return that

frosty valley Oct 3, 2022, 6:28 PM

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or return a pointer

rancid thunder Oct 3, 2022, 6:29 PM

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frosty valley or return a pointer

to some dynamically allocated memory or static memory?
way easier to just return a structure

#

also the way to declare a function returning an array would really be:

char f(char a[10])[10];

silent bobcat Oct 3, 2022, 6:29 PM

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shy fractal ```c char[10] palindrome_checker(char msg[10]){ return msg; } ``` how do we ...

can you even declare a function using "char[10]"

nocturne ventureBOT Oct 3, 2022, 6:29 PM

#

cdecl+

char f(char a[10])[10];

Declare f as function(array[10] of char named a) returning array[10] of char

Diagnostics

⛔ Return type may not be an array
ℹ Parameter of array type decays to pointer

shy fractal Oct 3, 2022, 6:30 PM

#

rancid thunder also the way to declare a function returning an array would really be: ```c char...

oh wait never seen this before

#

how do we return an array pointer again?

rancid thunder Oct 3, 2022, 6:31 PM

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shy fractal ```c char[10] palindrome_checker(char msg[10]){ return msg; } ``` how do we ...

char*palindrome_checker(char*msg){return msg;} would be way simpler

#

you should just write the pointer in the arguments

#

the array type will decay into a pointer type, this will make it clearer

shy fractal Oct 3, 2022, 6:32 PM

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char*palindrome_checker(char msg[10]){return msg;}

same same or?

rancid thunder Oct 3, 2022, 6:32 PM

#

equivalent but more confusing

shy fractal Oct 3, 2022, 6:32 PM

#

rancid thunder equivalent but more confusing

based

#

one last question

#

how would we read a string backward

#

msg[::-1]
boom i miss python

frosty valley Oct 3, 2022, 6:33 PM

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you just iterate from the last character to the first character

shy fractal Oct 3, 2022, 6:34 PM

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negative index?

frosty valley Oct 3, 2022, 6:34 PM

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nope.

shy fractal Oct 3, 2022, 6:34 PM

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hmmm ooh u saying assuming I know the total length right?

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backward for loop I c what u mean

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if msg[10] but the actual string length is 5 it won't work as expected orr

#

unless I use strlen() of course

rancid thunder Oct 3, 2022, 6:36 PM

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;compile

#include<string.h>
#include<stdio.h>
void foo(const char*s){
    const char*p=s+strlen(s);
    while(p!=s){
        printf("%c\n",(int)(unsigned char)*--p);
    }
}
int main(void){
    foo("abcd");
}

drowsy grottoBOT Oct 3, 2022, 6:36 PM

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Program Output

d
c
b
a

frosty valley Oct 3, 2022, 6:36 PM

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yeah, you will need to use strlen, unless you know the length already

rancid thunder Oct 3, 2022, 6:36 PM

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rancid thunder ;compile ```c #include<string.h> #include<stdio.h> void foo(const char*s){ c...

something like this?

silent bobcat Oct 3, 2022, 6:38 PM

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shy fractal how would we read a string backward

it can be something similar to this

    int i = 0;
    int j = len - 1;
    for (i = 0; i < len; i++){
        if (message[i] != message[j]){
            printf("Not Palindrome");
            break;
        }
        j--;
    }```

shy fractal Oct 3, 2022, 6:39 PM

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silent bobcat it can be something similar to this ``` int len = strlen(message); int i ...

hmm

#

we can use len - 1 directly inside the loop.

#

void palindrome_checker(char msg[10]){
    int len = strlen(msg);
    int j = len - 1; // last index
    for (int i = 0; i < len; i++){
        if (msg[i] != msg[j]){
            printf("Not Palindrome!\n");
            break;
        }
        printf("Palindrome!\n");
    }
}

#

Insert A string:
a7a
Palindrome!
Not Palindrome!

what's with the output!

#

!solved

stray laurelBOT Oct 3, 2022, 6:49 PM

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Thank you and let us know if you have any more questions!

silent bobcat Oct 3, 2022, 7:13 PM

#

!solved

#String User Input not working