isdigit

Is the function isdigit able to find digits that are in a string?
For example if I had a character string named string that contained the characters 34678904.

would

Code:

---

isdigit(string)

---

return a 0 since the character is a digit or would it return a nonzero b/c it recognizes it as something else?

If it returns a nonzero, what is a good way to check if a string is made up of characters or digits?

isdigit returns true if a character is one of 0123456789. You can check to see if a string consists solely of digits by looping over every element:

Code:

---

int anumber(char *s) {
  while (*s != '\0') {
    if (!isdigit(*s++))
      return 0;
  }

  return 1;
}

---

>Is the function isdigit able to find digits that are in a string?

Yes.

>would
> isdigit(string)
>return a 0

No. The function isdigit is used on a single character, not a string.

Code:

---

#include <stdio.h>
#include <ctype.h>

int main(void)
{
  const char text[] = "34678904 plus other stuff !5@#$";
  size_t i;
  for ( i = 0; i < sizeof text - 1; ++i )
  {
      if ( isdigit(text[i]) )
      {
        putchar(text[i]);
      }
  }
  putchar('\n');
  return 0;
}

/* my output
346789045
*/

---

>what is a good way to check if a string is made up of characters or digits?

If this is in the process of trying to convert a string representation of a number into an integer value, this may help.

thnaks guys you have been a big help