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strtoul, _strtoul_l, wcstoul, _wcstoul_l

Convert strings to an unsigned long-integer value.


unsigned long strtoul(
   const char *strSource,
   char **endptr,
   int base
unsigned long _strtoul_l(
   const char *strSource,
   char **endptr,
   int base,
   _locale_t locale
unsigned long wcstoul(
   const wchar_t *strSource,
   wchar_t **endptr,
   int base
unsigned long _wcstoul_l(
   const wchar_t *strSource,
   wchar_t **endptr,
   int base,
   _locale_t locale


Null-terminated string to convert.

Pointer to character that stops scan.

Number base to use.

Locale to use.

Return value

strtoul returns the converted value, if any, or ULONG_MAX on overflow. 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.

For more information about return codes, see errno, _doserrno, _sys_errlist, and _sys_nerr.


Each of these functions converts the input string strSource to an unsigned long.

strtoul stops reading the string strSource at the first character it can't recognize as part of a number. This character may be the terminating NULL, or it may be the first numeric character greater than or equal to base. The LC_NUMERIC category setting of the locale determines recognition of the radix character in strSource; for more information, see setlocale. strtoul and wcstoul use the current locale; _strtoul_l and _wcstoul_l are identical except that they use the locale passed in instead. For more information, see Locale.

If endptr isn't NULL, 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 were found or an invalid base was specified), the value of strSource is stored at the location pointed to by endptr.

wcstoul is a wide-character version of strtoul; its strSource argument is a wide-character string. Otherwise these functions behave identically.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Generic-text routine mappings

TCHAR.H routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_tcstoul strtoul strtoul wcstoul
_tcstoul_l strtoul_l _strtoul_l _wcstoul_l

strtoul expects strSource to point to a string of the following form:

[whitespace] [{+ | -}] [0 [{ x | X }]] [digits | letters]

A whitespace may consist of space and tab characters, which are ignored. digits are one or more decimal digits. letters are one or more of the letters a through z (or A through Z). The first character that doesn't fit this form stops the scan. If base is between 2 and 36, then it's used as the base of the number. If base is 0, the initial characters of the string pointed to by strSource are used to determine the base. If the first character is 0 and the second character isn't x or X, the string is interpreted as an octal integer. If the first character is '0' and the second character is x or X, the string is interpreted as a hexadecimal integer. If the first character is '1' through '9', the string is interpreted as a decimal integer. The letters a through z (or A through Z) are assigned the values 10 through 35; only letters whose assigned values are less than base are permitted. The first character outside the range of the base stops the scan. For example, if base is 0 and the first character scanned is '0', an octal integer is assumed and an '8' or '9' character will stop the scan. strtoul allows a plus (+) or minus (-) sign prefix; a leading minus sign indicates that the return value is negated.


Routine Required header
strtoul <stdlib.h>
wcstoul <stdlib.h> or <wchar.h>
_strtoul_l <stdlib.h>
_wcstoul_l <stdlib.h> or <wchar.h>

For more compatibility information, see Compatibility.


See the example for strtod.

See also

Data conversion
setlocale, _wsetlocale
String to numeric value functions
strtod, _strtod_l, wcstod, _wcstod_l
strtol, wcstol, _strtol_l, _wcstol_l
atof, _atof_l, _wtof, _wtof_l