Header File 

stdlib.h  

Category 

Conversion Routines, Math Routines 

Prototype 

unsigned long strtoul(const char *s, char **endptr, int radix); 

unsigned long wcstoul(const wchar_t *s, wchar_t **endptr, int radix); 

Description 

Converts a string to an unsigned long in the given radix. 

strtoul operates the same as strtol, except that it converts a string str to an unsigned long value (where strtol converts to a long). Refer to the entry for strtol for more information. 

Return Value 

strtoul returns the converted value, an unsigned long, or 0 on error. 

Example  

#include <stdlib.h>
#include <stdio.h>
int main(void)
{
   char *string = "87654321", *endptr;
   unsigned long lnumber;
   lnumber = strtoul(string, &endptr, 10);
   printf("string = %s  long = %lu\n",
   string, lnumber);
   return 0;
}

Portability