strtol, wcstol, _strtol_l, _wcstol_l

Convert strings to a long-integer value.


long strtol(
   const char *strSource,
   char **endptr,
   int base
long wcstol(
   const wchar_t *strSource,
   wchar_t **endptr,
   int base
long _strtol_l(
   const char *strSource,
   char **endptr,
   int base,
   _locale_t locale
long _wcstol_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

strtol returns the value represented in the string strSource, except when the representation would cause an overflow, in which case it returns LONG_MAX or LONG_MIN. strtol returns 0 if no conversion can be performed. wcstol returns values analogously to strtol. 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 these and other return codes.


The strtol function converts strSource to a long. strtol stops reading the string strSource 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.

wcstol is a wide-character version of strtol; its strSource argument is a wide-character string. These functions behave identically otherwise.

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

The current locale's LC_NUMERIC category setting determines recognition of the radix character in strSource; for more information, see setlocale. The functions without the _l suffix use the current locale; _strtol_l and _wcstol_l are identical to the corresponding functions without the _l suffix 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 strSource is stored at the location pointed to by endptr.

strtol 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 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 strSource 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.


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

For additional 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
strtoul, _strtoul_l, wcstoul, _wcstoul_l
atof, _atof_l, _wtof, _wtof_l