getchar() skip the first character when tried to scan the input

Question

I'm trying to scan the input from terminal and I'm trying to scan the initial white space but the program just skip it. I tried using this method before in a different program but it doesn't work in my new one. Plz help!!!

#include <stdio.h>
#include <string.h>

#define ADMIN_PASS "ABC123"
#define MAX_ARR_LEN 20
#define debug

void getinput(char inp[], int n);
void password(char passUser[]);

int main(void)
{      
    char passUser[MAX_ARR_LEN+1];
    int i=1;
    while (i==1)
    {
        password(passUser);
        printf("Try again?(1/0)>");
        scanf("%d",&i);
        if (i == 1)
        printf("\n");
    }
    return 0;
}

void getinput(char inp[], int n)
{
    scanf("%[^\n]c", &inp[n-1]);
    #ifdef debug
        printf("\nThe entered code in function>%s\n",inp);
        printf("The 1st character of entered code in function>%c\n",inp[0]);
    #endif
}

void password(char passUser[])
{
    char admin[MAX_ARR_LEN+1] = ADMIN_PASS;
    do
    {
        printf("\nPlease enter the Administrator password to Login:\n");
        getchar();
        getinput(passUser);
        #ifdef debug
            printf("\nThe input password in main is>%s\n", passUser);
            printf("The 1st character in main is>%c\n", passUser[0]);           
        #endif
        if (strcmp(passUser, admin) != 0)
        {
            printf("The password entered is incorrect, try again\n");
        }
    } while (!(strcmp(passUser, admin) == 0));   
}

it doesn't compile at all. getinput requires two args instead of one! I think you should start from this point — Nick S, Oct 05 '18 at 11:06
Copy/paste the actual code that you tested. If you do not, typos and other transcription errors will waste time and effort:( — Martin James, Oct 05 '18 at 11:10

Stefano Raneri · Answer 1 · 2018-10-06T15:04:23.663

0

You should pass the string with fgets(inp, sizeof(ADMIN_PASS), stdin) like this:

#include <stdio.h>
#include <string.h>

#define ADMIN_PASS "ABC123"
#define MAX_ARR_LEN 20
#define debug

void getinput(char * inp);
void password(char * passUser);

int main(void)
{
    char passUser[MAX_ARR_LEN+1];
    int i=1;
    while (i==1)
    {
        password(passUser);
        printf("Try again?(1/0)>");
        scanf("%d",&i);
        if (i == 1)
        printf("\n");
    }
    return 0;
}

void getinput(char * inp)
{
    fgets(inp, sizeof(ADMIN_PASS), stdin);
    #ifdef debug
        printf("\nThe entered code in function>%s\n",inp);
        printf("The 1st character of entered code in function>%c\n",inp[0]);
    #endif
}

void password(char * passUser)
{
    char admin[MAX_ARR_LEN+1] = ADMIN_PASS;
    do
    {
        printf("\nPlease enter the Administrator password to Login:\n");
        getinput(passUser);
        #ifdef debug
            printf("\nThe input password in main is>%s\n", passUser);
            printf("The 1st character in main is>%c\n", passUser[0]);
        #endif
        if (strcmp(passUser, admin) != 0)
        {
            printf("The password entered is incorrect, try again\n");
        }
    } while (!(strcmp(passUser, admin) == 0));
}

I removed getchar() and the second parameter of the function getinput() cause they were useless.

edited Oct 06 '18 at 15:04

answered Oct 05 '18 at 11:36

Stefano Raneri

323
4
14

I tried compling it on terminal and tried a sample input " ABC 123". It doesn't recognize the 1st white space – hry0918 Oct 05 '18 at 13:58
Ops, my bad, i think a better solution is to use fgets instead of scanf, cause if you do scanf("%[^\n]", inp), with the first character as a whitespace, it produces a loop error. So it's better instead to use fgets(inp, MAX_ARR_LEN, stdin). Now it should work. – Stefano Raneri Oct 05 '18 at 16:29
You're welcome, feel free to upvote my answer, or mark it as the solution. – Stefano Raneri Oct 06 '18 at 12:33
Hey, I tried using the fgets but i ran into a problem when compling it. Because the parameter is MAX_ARRAY_LEN, it cause the input to be different from the admin password. When I entered the correct password, it prompts the message wrong password – hry0918 Oct 06 '18 at 12:42
1

Instead of MAX_ARR_LEN use sizeof(ADMIN_PASS). – Stefano Raneri Oct 06 '18 at 15:04

getchar() skip the first character when tried to scan the input

1 Answers1