Convert strings to a long-integer value.
long strtol( const char *nptr, char **endptr, int base ); long wcstol( const wchar_t *nptr, wchar_t **endptr, int base );
strtol returns the value represented in the string nptr, 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 nptr to a long. strtol 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.
wcstol is a wide-character version of strtol; 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 |
---|---|---|---|
_tcstol | strtol | strtol | wcstol |
The current locale's LC_NUMERIC category setting determines recognition of the radix character in nptr; for more information, see setlocale. 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.
strtol 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; otherwise, it is interpreted as a decimal number. 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.
Routine | Required header | Compatibility |
---|---|---|
strtol | <stdlib.h> | ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP |
wcstol | <stdlib.h> or <wchar.h> | ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
All versions of the C run-time libraries.
Convert strings to a double-precision value.
double strtod( const char *nptr, char **endptr ); double wcstod( const wchar_t *nptr, wchar_t **endptr );
strtod returns the value of the floating-point number, except when the representation would cause an overflow, in which case the function returns +/–HUGE_VAL. The sign of HUGE_VAL matches the sign of the value that cannot be represented. strtod returns 0 if no conversion can be performed or an underflow occurs.
wcstod returns values analogously to strtod. 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.
Each function converts the input string nptr to a double. The strtod function converts nptr to a double-precision value. strtod stops reading the string nptr at the first character it cannot recognize as part of a number. This may be the terminating null character. wcstod is a wide-character version of strtod; 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 |
---|---|---|---|
_tcstod | strtod | strtod | wcstod |
The LC_NUMERIC category setting of the current locale determines recognition of the radix character in nptr; for more information, see setlocale. 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.
strtod expects nptr to point to a string of the following form:
[whitespace] [sign] [digits] [.digits] [ {d | D | e | E}[sign]digits]
A whitespace may consist of space and tab characters, which are ignored; sign is either plus (+) or minus (–); and digits are one or more decimal digits. If no digits appear before the radix character, at least one must appear after the radix character. The decimal digits can be followed by an exponent, which consists of an introductory letter (d, D, e, or E) and an optionally signed integer. If neither an exponent part nor a radix character appears, a radix character is assumed to follow the last digit in the string. The first character that does not fit this form stops the scan.
Routine | Required header | Compatibility |
---|---|---|
strtod | <stdlib.h> | ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP |
wcstod | <stdlib.h> or <wchar.h> | ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
All versions of the C run-time libraries.
// crt_strtod.c /* This program uses strtod to convert a * string to a double-precision value; strtol to * convert a string to long integer values; and strtoul * to convert a string to unsigned long-integer values. */ #include <stdlib.h> #include <stdio.h> int main( void ) { char *string, *stopstring; double x; long l; int base; unsigned long ul; string = "3.1415926This stopped it"; x = strtod( string, &stopstring ); printf( "string = %s/n", string ); printf(" strtod = %f/n", x ); printf(" Stopped scan at: %s/n/n", stopstring ); string = "-10110134932This stopped it"; l = strtol( string, &stopstring, 10 ); printf( "string = %s/n", string ); printf(" strtol = %ld/n", l ); printf(" Stopped scan at: %s/n/n", stopstring ); string = "10110134932"; printf( "string = %s/n", string ); /* Convert string using base 2, 4, and 8: */ for( base = 2; base <= 8; base *= 2 ) { /* Convert the string: */ ul = strtoul( string, &stopstring, base ); printf( " strtol = %ld (base %d)/n", ul, base ); printf( " Stopped scan at: %s/n", stopstring ); } }
string = 3.1415926This stopped it strtod = 3.141593 Stopped scan at: This stopped it string = -10110134932This stopped it strtol = -2147483648 Stopped scan at: This stopped it string = 10110134932 strtol = 45 (base 2) Stopped scan at: 34932 strtol = 4423 (base 4) Stopped scan at: 4932 strtol = 2134108 (base 8) Stopped scan at: 932