input checking

[estranged]

hi

i need to check that correct input is given to my prog.

i need to input a student number containing only 6 integers (e.g. 123456) and nothing else
in case something else is typed in the prog should just repet the request for a 6 integer string or something like that

how do i do this in c?

thank you

[Prelude]

int digits, copy = input;
for ( digits = 0; copy != 0; copy /= 10 )
  ++digits;
if ( digits != 6 )
  printf ( "Error: Invalid input\n" );

-Prelude

[Monster]

char input[100];
int i;
do
{
    printf("Give number: ");
    scanf("%s", input);
    for(i = 0; input[i] && isdigit(input[i]); i++) ;
} while(i != 6 || input[i]);