Checking whether input is number in C - c

Question

I need to check whether the input is number. My code looks something like this:
int input;
while ( scanf(" %s %d", string, &input) != EOF) {
if ( isNotANumber(input) ) {
printf("Not a number"); }
doSomethingElse(input, string);
}
EDIT: I need to be accepting input and calling the function doSomethingElse(input) until the user enters EOF.
isNotANumber is a mock function, I don't have that function, I'm asking how could I write it.
EDIT 2: Variable string needs to be a string, variable input needs to be an integer.
EDIT 3: I tried separating my code into this:
while (scanf(" %s", string) != EOF) {
if (scanf("%d",&input) != 1) {
printf("not a number");
}
doSomething();
}
But it stil doesn't work for input like "4a".

Answer 1

For example, you can change it as follows.
#include <stdio.h>
#define doSomethingElse(input) do{ printf("your input is %d\n", input); }while(0)
int main(void){
int input;
int status;
while ((status = scanf("%d", &input)) != EOF) {
if ( status == 0 ) {
printf("Not a number\n");
while(getchar() != '\n'); //clear input
}
else {
doSomethingElse(input);
}
}
}
However, this can not check input like 123.456. (accept 123)
So, It is recommended to input with fgets and check with strtol.
As already pointed out, like scanf(" %s %d", string, &input) can not check the input after the number.
So, For convenience, check backward input.
char string[32], ch;
int input;
int status;
while ((status = scanf("%31s %d%c", string, &input, &ch )) != EOF) {
if ( status == 3 && ch == '\n') {
doSomethingElse(input);
}
else {
printf("Not a number\n");
while(getchar() != '\n'); //clear input
}
}
Example using fgets and strtol
(mystrtoi has reorganized the answer of chux. thanks)
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#define doSomethingElse(input) do{ printf("your input is %d\n", input); }while(0)
int mystrtoi(const char *str, int *err) {
char *endptr;
*err = errno = 0;
long l = strtol(str, &endptr, 0);
if (errno == ERANGE || *endptr != '\0' || str == endptr) {
*err = 1;
}
// Only needed if sizeof(int) < sizeof(long)
if (l < INT_MIN || l > INT_MAX) {
*err = 1;
}
return (int) l;
}
int main(void){
char line[128];
char string1[32], string2[128];
int num, err;
while (fgets(line, sizeof line, stdin)){
// if(2 != sscanf(line, "%31s %31s", string1, string2)){// or use strtok to split
if(2 != sscanf(line, "%31s %127[^\n]", string1, string2)){
printf("invalid input\n");
continue;
}
num = mystrtoi(string2, &err);
if(err) {
printf("Not a number\n");
}
else {
doSomethingElse(num);
}
}
}

Answer 2

while ( scanf("%d", input) != EOF)
Your scanf code has two problems:
scanf returns the number of successfully read item, not EOF. Here you want to check if scanf has successfully read one integer input
scanf expects the address of the variable
You should re-write that line as:
while ( scanf("%d", &input) == 1 )