atol-atol-l-wtol-wtol-l.md

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atol, _atol_l, _wtol, _wtol_l | Microsoft Docs		11/04/2016			cpp-standard-libraries		article	atol _wtol_l _wtol _atol_l	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-convert-l1-1-0.dll	DLLExport	_atol_l _ttol_l _tstol_l _tstol _wtol _ttol _wtol_l	C++	tstol function atol function ttol function _atol_l function _tstol_l function string conversion, to integers _tstol function _ttol function _ttol_l function atol_l function wtol_l function _wtol_l function wtol function _wtol function	cedfc21c-2d64-4e9c-bd04-bdf60b12db46	22	corob-msft	corob	ghogen

atol, _atol_l, _wtol, _wtol_l

Convert a string to a long integer.

Syntax

long atol(  
   const char *str   
);  
long _atol_l(  
   const char *str,  
   _locale_t locale  
);  
long _wtol(  
   const wchar_t *str   
);  
long _wtol_l(  
   const wchar_t *str,  
   _locale_t locale  
);  

Parameters

str
String to be converted.

locale
Locale to use.

Return Value

Each function returns the long value produced by interpreting the input characters as a number. The return value is 0L for atol if the input cannot be converted to a value of that type.

In the case of overflow with large positive integral values, atol returns LONG_MAX; in the case of overflow with large negative integral values, LONG_MIN is returned. In all out-of-range cases, errno is set to ERANGE. If the parameter passed in is NULL, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, these functions set errno to EINVAL and return 0.

Remarks

These functions convert a character string to a long integer value (atol).

The input string is a sequence of characters that can be interpreted as a numerical value of the specified type. The function stops reading the input string at the first character that it cannot recognize as part of a number. This character may be the NULL character ('\0' or L'\0') terminating the string.

The str argument to atol has the following form:

[whitespace] [sign] [digits]]

A whitespace consists of space or tab characters, which are ignored; sign is either plus (+) or minus (-); and digits are one or more digits.

_wtol is identical to atol except that it takes a wide character string.

The versions of these functions with the _l suffix are identical except that they use the locale parameter passed in instead of the current locale. For more information, see Locale.

Generic-Text Routine Mappings

TCHAR.H routine	_UNICODE & _MBCS not defined	_MBCS defined	_UNICODE defined
_tstol	atol	atol	_wtol
_ttol	atol	atol	_wtol

Requirements

Routines	Required header
atol	<stdlib.h>
_atol_l, _wtol, _wtol_l	<stdlib.h> and <wchar.h>

Example

This program shows how numbers stored as strings can be converted to numeric values using the atol function.

// crt_atol.c  
// This program shows how numbers stored as  
// strings can be converted to numeric values  
// using the atol functions.  
#include <stdlib.h>  
#include <stdio.h>  
#include <errno.h>  
  
int main( void )  
{  
    char    *str = NULL;  
    long    value = 0;  
  
    // An example of the atol function  
    // with leading and trailing white spaces.  
    str = "  -2309 ";  
    value = atol( str );  
    printf( "Function: atol( \"%s\" ) = %d\n", str, value );  
  
    // Another example of the atol function   
    // with an arbitrary decimal point.  
    str = "314127.64";  
    value = atol( str );  
    printf( "Function: atol( \"%s\" ) = %d\n", str, value );  
  
    // Another example of the atol function  
    // with an overflow condition occurring.  
    str = "3336402735171707160320";  
    value = atol( str );  
    printf( "Function: atol( \"%s\" ) = %d\n", str, value );  
    if (errno == ERANGE)  
    {  
       printf("Overflow condition occurred.\n");  
    }  
}  

Function: atol( "  -2309 " ) = -2309  
Function: atol( "314127.64" ) = 314127  
Function: atol( "3336402735171707160320" ) = 2147483647  
Overflow condition occurred.  

See Also

Data Conversion
Floating-Point Support
Locale
_ecvt
_fcvt
_gcvt
setlocale, _wsetlocale
_atodbl, _atodbl_l, _atoldbl, _atoldbl_l, _atoflt, _atoflt_l