C strtoul() function

C strtoul() function - Convert a string to an unsigned long

Syntax strtoul() function

unsigned long int strtoul(const char *str, char **endptr, int base)

The strtoul() function is used to convert a character string to an unsigned long integer value. The parameter str points to a sequence of characters that can be interpreted as a numeric value of type unsigned long int.

Parameters strtoul() function

Return value from strtoul()

This function returns the converted integral number as a long int value. If no valid conversion could be performed, a zero value is returned.

• Upon successful completion, these functions shall return the converted value, if any.
• Returns 0 if base has an invalid value (less than 0, 1, or greater than 36)

Example: strtoul() function

The following example shows the usage of strtoul() function.

#include <stdio.h>
#include <stdlib.h>
 
#define BASE2 2
#define BASE4 4
 
int main(void)
{
   char *string, *stopstring;
   unsigned long ul;
 
   string = "1000e12 e";
   printf("Original string = %s\n", string);
   ul = strtoul(string, &stopstring, BASE2);
   printf("strtoul = %ld (base %d)\n", ul, BASE2);
   printf("Stopped scan at %s\n\n", stopstring);
   string = "10000000e12 e";
   printf("Original string = %s\n", string);
   ul = strtoul(string, &stopstring, BASE2);
   printf("strtoul = %ld (base %d)\n", ul, BASE4);
   printf("Stopped scan at %s\n\n", stopstring);
} 

Output:

Original string = 1000e12 e
strtoul = 8 (base 2)
Stopped scan at e12 e

Original string = 10000000e12 e
strtoul = 128 (base 4)
Stopped scan at e12 e

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