Converts a string to an unsigned long integer value.

#include <stdlib.h>

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

#include <wchar.h>

unsigned long wcstoul(const wchar_t *nptr, wchar_t **endptr, int base);

Parameters

nptr

String to convert; a sequence of characters that can be interpreted as a numerical value of the specified type.

endptr

End of scan.

base

Number base to use.

Remarks

strtoul expects nptr to point to a string with this form:

[whitespace][sign][0][{x|X}][digits]

These functions stop reading the string at the first character they cannot recognize as part of a number. This may be the null character \0 at the end of the string. With strtoul, this terminating character can also be the first numeric character greater than or equal to base. If endptr is not a null pointer, a pointer to the character that stopped the scan is stored at the location pointed to by endptr.

If no conversion can be performed (no valid digits are found or an invalid base is specified), the value of nptr is stored at the location pointed to by endptr.

strtoul allows a plus (+) or minus (-) sign prefix; a leading minus sign indicates that the return value is negated.

Return Values

strtoul returns the value represented in the string nptr, except when the representation would cause an overflow, in which case it returns LONG_MAX or LONG_MIN. strtoul returns 0 if no conversion can be performed.

wcstoul returns values analogously to strtoul. For both functions, errno is set to ERANGE if overflow or underflow occurs.

Generic Text Routines

Requirements