Need basic help in C with

Question

There is the validating function for my size which i can't manage to code it properly

    void getsize(int* size, int cap){
    while(1){
    printf("Enter the size(whole number) of array from interval (0, %d]: \n", cap);
   if (scanf("%d", size) == 1){
    if ((*size > 1) && (*size <= cap)){
            printf("Size: %d entered\n", *size);
            break;
        } else {
            printf("Invalid size. Try again.\n");
        }
    } else {
        printf("Invalid size. Try again.\n");
        break;
    }
    }
}

What I expect from user is to enter positive whole number. Can anybody fix this or show better solution for this? Thanks.

Please be more specific as to what issues you are running into. Otherwise it will be tough for others to help you. — Buddha, Apr 13 '14 at 17:50
Perhaps you are mistakenly using `break` when you shouldn't use it? — Some programmer dude, Apr 13 '14 at 17:58

perreal · Accepted Answer · 2014-04-13T18:06:47.993

Your version may accept float numbers since the part before the dot is a valid integer. Instead you can use strtol and check the end of the number is indeed a newline:

#include <stdio.h>
#include <stdlib.h>
void getsize(int* size, int cap){
    char buffer[256], *c;
    while (1) {
        if (fgets(buffer, sizeof(buffer), stdin)) {
            int lsize = strtol(buffer, &c, 10);
            if ((lsize > 1) && (lsize <= cap) && c[0] == '\n'){
                printf("Size: %d %s entered\n", lsize, c);
                *size = lsize;
                return;
            } 
        }
        printf("Invalid size. Try again.\n");
    }
}

int main ( ) {  
    int size;
    getsize(&size, 10);
    return 0;
}

`atoi` isn't a function I would recommend, as you can't differentiate between an invalid number in the string and zero. Instead I'd recommend [`strtol`](http://en.cppreference.com/w/c/string/byte/strtol). Though I admit that in this case it really doesn't matter as zero is invalid in any case. — Some programmer dude, Apr 13 '14 at 18:05

score 0 · Answer 2 · answered Apr 13 '14 at 18:04

I can't see any use of receiving size as a parameter to getsize since u only need the limits which can be provided by "cap" itself.Secondly,an address to a variable is to be provided to scanf.

void getsize(int cap){
   int size;
while(1){
printf("Enter the size(whole number) of array from interval (0, %d]: \n", cap);
if (scanf("%d", &size) == 1){
if ((size > 1) && (size <= cap)){
        printf("Size: %d entered\n", *size);
        break;
    } else {
        printf("Invalid size. Try again.\n");
    }
} else {
    printf("Invalid size. Try again.\n");
    break;
}
}
}

Need basic help in C with

2 Answers2