How to read a number with leading 0's as one int using scanf in C?

Question

I am using C to read integer data using scanf("%i", &myInt). I know for this particular input the data will ALWAYS be three digits. However, sometimes I need to read a number with leading 0's like 001 or 078. When scanf() reads a number with a leading zero it will not pick up the subsequent digits. For example, when I read 078 scanf reads 7 then the next scanf will read the 8. I would like scanf to read 78. Can someone tell me how to do this properly? Here is a code example:

int x;

while (scanf("%i", &x) != EOF) {

   //do operations on each of the digits

}

Answer 1

I suspect you may be using the %i conversion specifier which honors C conventions like 0x denoting hex, and leading zeros denoting octal. If the input is 078 and %i is used, then only 07 matches because 8 is not an octal digit. Use %d to scan decimal integers.

The i in %i does not mean "reach for me whenever you need to convert an i)nteger to type i)nt".

The width is only necessary if the three digit number is followed by more digits which we need to exclude from the scan. For instance, we can convert a date given as "20140417" into three integers using the format string "%4d%2d%d". The last %d could be %2d but doesn't have to be. These values do not specify how many digits to extract, but rather they specify a maximum field width: the conversion takes up to that many characters (including a possible plus or minus sign). For the input -1234, the %3d conversion will take -12, and leave the 34. For the input 1$, %3d will just take the 1 and leave the $, because it isn't a decimal digit.

Answer 2

You can use a width delimiter with scanf, even on integer types :

int i;
scanf ("%3d",&i); // Will read 3 characters and interpret them as an integer