CODEWITHSUNDEEP
c++c
user2975955
user2975955

Reputation: 1

How to prevent my input jump to other function as the program continue

My problem is when i input more than 1 number or characters(ex:156) the value 56 directly go to my next function ( f1, f2 ). How can i prevent that and print out that is an error ? (p.s : i'm new so if you guys can help me w/o using iostream, it'd be great

char c;
printf("menu");
printf("Please enter the option 1 - 4, press q to quit\n");
input_c:            
scanf("%c",&c);
do{         
switch (c)          
case '1': f1();
break;
case '2': f2();
break;
case 'q': quit();
break;
default: goto input_c;
break;
}

i edited this as my original code which lead me to the same problem

Upvotes: 0

Views: 83

Answers (3)

Sunil Bojanapally
Sunil Bojanapally

Reputation: 12658

In char c[2]; declaration, c is a array of 2 characters ranging from index 0 to 1. So while reading the input into it, scanf("%c", &c[i]) should be used.

You cannot use array index as 2 in statement switch (c[2]), since array indexing starts from 0 in C. 

main() {
char c; 
scanf("%c", &c);
switch(c) {
   case '1': f1(); break;
   case '2': f2(); break;
   case 'q': quit(); break;
   default: //blah
}

The above method can be employed with simplicity.

Upvotes: 1

masoud
masoud

Reputation: 56479

You're reading a character so, strlen on it is not correct and will make undefined behavior. Second, your array size is 2, so you can index it by 0 and 1. c[2] can invoke undefined behavior again.

Just use a simple character variable instead and replace goto by while:

char c;

while(true)
{
    scanf("%c",&c); // cin >> c;

    switch (c)
    {
    case '1':
        f1();
        break;
    case '2':
        f2();
        break;
    case 'q':
        quit();
        break;
    }
}

Upvotes: 0

user2699298
user2699298

Reputation: 1476

The reason of this behavior is because you declared an array of chars [2] and you're only using one of its elements (first). So when you input 145, it takes the 1 only and that's why it goes to the first function.

Upvotes: 0

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