Some help to understand.

**Sietor** · 08-17-2016

So I am making this basic game in C, And when I type in more than 1 character in the scanf part it read as example:

Where would you like to go:
ERASF <---- This is what the user types.
You are in your house
You are in your house
You are in your house
You are in your house
You are in your house

This is the code:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>

int main()
{

    char Move;
    float LocationA = 0;
    float LocationB = 0;

    printf("\n\n\nWhere would you like to go?\n");
    do{

        scanf(" %s", &Move);

        if(Move == 'E'){
            LocationB++;
        }
        if(Move == 'W'){
            LocationB--;
        }
        if(Move == 'S'){
            LocationA--;
        }
        if(Move == 'N'){
            LocationA++;
        }
        if(LocationA == 0 && LocationB == 0){
            printf("You are in your house\n");
        }
        if(LocationA == 0 && LocationB == 1){
            printf("You are on a road\n");
            continue;
        }
        if(LocationA == 1 && LocationB == 0){
            printf("You are in a forest");
            continue;
        }
        if(LocationA == 0 && LocationB == -1){
            printf("You are in a forest\n");
            continue;
        }
        if(LocationA == -1 && LocationB == 0){
            printf("You are in a forest\n");
            continue;
        }

    }while(Move != 'M');

    return 0;
}

Can I make the program Only read what the user types, if there is only 1 character?
And how?
And why does it reply on every character I write in the scanf instead of just the 1 time?

Ask if you dont understand the questions and i will try to explain more.

**Sietor** · 08-17-2016

I have edited the post

**Sietor** · 08-17-2016

Where would you like to go?
Home <---- User
You are in your house
Really? <----User
You are in your house
Why am i home <--- User
You are in a forest
You are in a forest
You are in a forest
You are in a forest

Efter the edited code this are the responses i get after typing in what the User point at.
and why is it so?

**Elkvis** · 08-17-2016

One major problem I see is that in your scanf call, you're asking for a string, but only giving it a single char to read into. This will cause undefined behavior. You really need to use %c instead of %s.

**jimblumberg** · 08-17-2016

What did you not understand from this topic?

You're still not using the correct format specifier for your scanf() call, which produces undefined behavior.

And in future please don't open a new topic when you already have a topic open for the problem.

Jim

**Sietor** · 08-17-2016

Ok wont happen again Jim!
Elkvis even if I change the %s to a %c i get the same problem... as fast as i put a space between two characters, it gives me multiple anwsers.

**Elkvis** · 08-17-2016

Originally Posted by Sietor

Elkvis even if I change the %s to a %c i get the same problem...

My response wasn't intended to solve the problem that you're asking about. Only to make your program more semantically correct.

**Sietor** · 08-17-2016

OK!
Thanks Elkvis

**amadeus777999** · 08-19-2016

I've prepared this little routine for you...
be aware that

Code:

getchar()

instead of

Code:

scanf(...)

is used in combination with

Code:

fflush()

.
This enables a little more robust program behavior as user input is limited to the first character on a line and no dangling input remaining, which may cause undefined behavior. No guarantees though.

Code:

void Getchar_Test( void )
{
    const char    s[3][3][16] =    { 
                                    { { "Road" }, { "Road" }, {"Forest"} } , 
                                    { { "Shed" }, { "House" }, {"Road"} } , 
                                    { { "Road" }, { "Jeep" }, {"Corpse!"} } , 
                                }, 
                s_blocked[] = "Your way is blocked...",
                c_exit = 'q';
    const int    ox = 1, oy = 1;
    int            x = 0, y = 0, 
                c, moves;
    
    
    printf("Possible commands...\n\t\t(n)orth, (w)est, (s)outh, (e)ast, (i)nventory, (q)uit.\n\n");
    printf( "(n, w, s, e, i or %c)? ", c_exit );
    c = getchar();
    c = toupper( c );
    for ( moves = 0; toupper(c_exit) != c; moves++ )
    {
        switch( c )
        {
            case 'N': 
                if (-1 < y) { y--; } else { printf("\t%s\n", s_blocked); }
                break;
            case 'W':
                if (-1 < x) { x--; } else { printf("\t%s\n", s_blocked); }
                break;
            case 'S':
                if (1 > y) { y++; } else { printf("\t%s\n", s_blocked); }
                break;
            case 'E':
                if (1 > x) { x++; } else { printf("\t%s\n", s_blocked); }
                break;
            case 'I':
                printf( "\tYou carry... %s.\n", "nothing" );
                break;
            default:
                printf("Unknown command...\n");
        }
        
        printf("\n[Move %d]\n\tYou are at... %s\n\n", moves + 1, s[oy+y][ox+x] );
        
        printf( "(n, w, s, e, i or %c)? ", c_exit );
        fflush( stdin );    /* remove newline ...and other possible characters not needed */
        c = getchar();
        c = toupper( c );
    }
    
    printf("\n\n\nAfter %4i move(s)... your adventure is over.\n", moves );
}

**whiteflags** · 08-19-2016

FAQ > Why fflush(stdin) is wrong - Cprogramming.com

**jimblumberg** · 08-19-2016

fflush( stdin ); /* remove newline ...and other possible characters not needed */

Don't you mean, produces undefined behavior? The fflush() function is only defined by the standard to work with output streams, using it on an input stream produces undefined results.

Jim

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