strtol, wcstol, _strtol_l, _wcstol_l

Convert strings to a long integer value.

Syntax

long strtol(
   const char *string,
   char **end_ptr,
   int base
);
long wcstol(
   const wchar_t *string,
   wchar_t **end_ptr,
   int base
);
long _strtol_l(
   const char *string,
   char **end_ptr,
   int base,
   _locale_t locale
);
long _wcstol_l(
   const wchar_t *string,
   wchar_t **end_ptr,
   int base,
   _locale_t locale
);

Parameters

string
Null-terminated string to convert.

end_ptr
An output parameter, set to point to the character after the last interpreted character. Ignored, if NULL.

base
Number base to use.

locale
Locale to use.

Return Value

strtol, wcstol, _strtol_l, and _wcstol_l return the value represented in string. They return 0 if no conversion is possible. When the representation would cause an overflow, they return LONG_MAX or LONG_MIN.

errno is set to ERANGE if overflow or underflow occurs. It's set to EINVAL if string is NULL. Or, if base is nonzero and less than 2, or greater than 36. For more information on ERANGE, EINVAL, and other return codes, see _doserrno, errno, _sys_errlist, and _sys_nerr.

Remarks

The strtol, wcstol, _strtol_l, and _wcstol_l functions convert string to a long. They stop reading string at the first character not recognized as part of a number. It may be the terminating-null character, or the first alphanumeric character greater than or equal to base.

wcstol and _wcstol_l are wide-character versions of strtol and _strtol_l. Their string argument is a wide-character string. These functions behave identically to strtol and _strtol_l otherwise. The locale's LC_NUMERIC category setting determines recognition of the radix character (the fractional marker or decimal point) in string. The functions strtol and wcstol use the current locale. _strtol_l and _wcstol_l use the locale passed in instead. For more information, see [setlocale] and Locale.

When end_ptr is NULL, it's ignored. Otherwise, a pointer to the character that stopped the scan is stored at the location pointed to by end_ptr. No conversion is possible if no valid digits are found, or an invalid base is specified. The value of string is then stored at the location pointed to by end_ptr.

strtol expects string to point to a string of the following form:

[whitespace] [{+ | -}] [0 [{ x | X }]] [alphanumerics]

Square brackets ([ ]) surround optional elements. Curly braces and a vertical bar ({ | }) surround alternatives for a single element. whitespace may consist of space and tab characters, which are ignored. alphanumerics are decimal digits or 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 string 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. The scan only allows letters whose values are less than base. The first character outside the range of the base stops the scan. For example, suppose string starts with "01". If base is 0, the scanner assumes it's an octal integer. An '8' or '9' character stops the scan.

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

Generic-Text Routine Mappings

TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined
_tcstol strtol strtol wcstol
_tcstol_l _strtol_l _strtol_l _wcstol_l

Requirements

Routine Required header
strtol <stdlib.h>
wcstol <stdlib.h> or <wchar.h>
_strtol_l <stdlib.h>
_wcstol_l <stdlib.h> or <wchar.h>

The _strtol_l and _wcstol_l functions are Microsoft-specific, not part of the Standard C library. For additional compatibility information, see Compatibility.

Example

See the example for strtod.

See also

Data conversion
Locale
localeconv
setlocale, _wsetlocale
String to numeric value functions
strtod, _strtod_l, wcstod, _wcstod_l
strtoll, _strtoll_l, wcstoll, _wcstoll_l
strtoul, _strtoul_l, wcstoul, _wcstoul_l
atof, _atof_l, _wtof, _wtof_l