Originální popis anglicky:
strtol, strtoll, strtoq - convert a string to a long integer
Návod, kniha: Linux Programmer's Manual
#include <stdlib.h>
long int
strtol(const char *nptr, char **endptr, int base);
long long int
strtoll(const char *nptr, char **endptr, int base);
The
strtol() function converts the initial part of the string in
nptr to a long integer value according to the given
base, which
must be between 2 and 36 inclusive, or be the special value 0.
The string must begin with an arbitrary amount of white space (as determined by
isspace(3)) followed by a single optional `+' or `-' sign. If
base is zero or 16, the string may then include a `0x' prefix, and the
number will be read in base 16; otherwise, a zero
base is taken as 10
(decimal) unless the next character is `0', in which case it is taken as 8
(octal).
The remainder of the string is converted to a long int value in the obvious
manner, stopping at the first character which is not a valid digit in the
given base. (In bases above 10, the letter `A' in either upper or lower case
represents 10, `B' represents 11, and so forth, with `Z' representing 35.)
If
endptr is not NULL,
strtol() stores the address of the first
invalid character in
*endptr. If there were no digits at all,
strtol() stores the original value of
nptr in
*endptr
(and returns 0). In particular, if
*nptr is not `\0' but
**endptr is `\0' on return, the entire string is valid.
The
strtoll() function works just like the
strtol() function but
returns a long long integer value.
The
strtol() function returns the result of the conversion, unless the
value would underflow or overflow. If an underflow occurs,
strtol()
returns LONG_MIN. If an overflow occurs,
strtol() returns LONG_MAX. In
both cases,
errno is set to ERANGE. Precisely the same holds for
strtoll() (with LLONG_MIN and LLONG_MAX instead of LONG_MIN and
LONG_MAX).
- EINVAL
- (not in C99) The given base contains an unsupported
value.
- ERANGE
- The resulting value was out of range.
The implementation may also set
errno to
EINVAL in case no
conversion was performed (no digits seen, and 0 returned).
In locales other than the "C" locale, also other strings may be
accepted. (For example, the thousands separator of the current locale may be
supported.)
BSD also has
quad_t
strtoq(const char *nptr, char **endptr, int base);
with completely analogous definition. Depending on the wordsize of the current
architecture, this may be equivalent to
strtoll() or to
strtol().
strtol() conforms to SVID 3, BSD 4.3, ISO 9899 (C99) and POSIX, and
strtoll() to ISO 9899 (C99) and POSIX 1003.1-2001.
atof(3),
atoi(3),
atol(3),
strtod(3),
strtoul(3)
