strtoul, _strtoul_l, wcstoul, _wcstoul_l

發行項
12/18/2017

The latest version of this topic can be found at strtoul, _strtoul_l, wcstoul, _wcstoul_l.

Convert strings to an unsigned long-integer value.

Syntax

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

Parameters

nptr
Null-terminated string to convert.

endptr
Pointer to character that stops scan.

base
Number base to use.

locale
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.

See _doserrno, errno, _sys_errlist, and _sys_nerr for more information on this, and other, return codes.

Remarks

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

strtoul stops reading the string nptr at the first character it cannot recognize as part of a number. This may be the terminating null character, 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 nptr; 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 is not 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 nptr is stored at the location pointed to by endptr.

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

Generic-Text Routine Mappings

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

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

[whitespace] [{+ | –}] [0 [{ x | X }]] [digits]

A whitespace may consist of space and tab characters, which are ignored; digits are one or more decimal digits. The first character that does not fit this form stops the scan. If base is between 2 and 36, then it is used as the base of the number. If base is 0, the initial characters of the string pointed to by nptr are used to determine the base. If the first character is 0 and the second character is not '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.

Requirements

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

For additional compatibility information, see Compatibility in the Introduction.

Example

See the example for strtod.

.NET Framework Equivalent

System::Convert::ToUInt64

共用方式為