преобразовать строку в длинное целое число (convert a string to a long integer)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
strtol, strtoll — convert a string to a long integer
Синопсис (Synopsis)
#include <stdlib.h>
long strtol(const char *restrict nptr, char **restrict endptr, int base);
long long strtoll(const char *restrict nptr, char **restrict endptr,
int base)
Описание (Description)
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
These functions shall convert the initial portion of the string
pointed to by nptr to a type long and long long representation,
respectively. First, they decompose the input string into three
parts:
1. An initial, possibly empty, sequence of white-space
characters (as specified by isspace())
2. A subject sequence interpreted as an integer represented in
some radix determined by the value of base
3. A final string of one or more unrecognized characters,
including the terminating NUL character of the input string.
Then they shall attempt to convert the subject sequence to an
integer, and return the result.
If the value of base is 0, the expected form of the subject
sequence is that of a decimal constant, octal constant, or
hexadecimal constant, any of which may be preceded by a '+' or
'-' sign. A decimal constant begins with a non-zero digit, and
consists of a sequence of decimal digits. An octal constant
consists of the prefix '0' optionally followed by a sequence of
the digits '0' to '7' only. A hexadecimal constant consists of
the prefix 0x or 0X followed by a sequence of the decimal digits
and letters 'a' (or 'A') to 'f' (or 'F') with values 10 to 15
respectively.
If the value of base is between 2 and 36, the expected form of
the subject sequence is a sequence of letters and digits
representing an integer with the radix specified by base,
optionally preceded by a '+' or '-' sign. The letters from 'a'
(or 'A') to 'z' (or 'Z') inclusive are ascribed the values 10 to
35; only letters whose ascribed values are less than that of base
are permitted. If the value of base is 16, the characters 0x or
0X may optionally precede the sequence of letters and digits,
following the sign if present.
The subject sequence is defined as the longest initial
subsequence of the input string, starting with the first non-
white-space character that is of the expected form. The subject
sequence shall contain no characters if the input string is empty
or consists entirely of white-space characters, or if the first
non-white-space character is other than a sign or a permissible
letter or digit.
If the subject sequence has the expected form and the value of
base is 0, the sequence of characters starting with the first
digit shall be interpreted as an integer constant. If the subject
sequence has the expected form and the value of base is between 2
and 36, it shall be used as the base for conversion, ascribing to
each letter its value as given above. If the subject sequence
begins with a <hyphen-minus>, the value resulting from the
conversion shall be negated. A pointer to the final string shall
be stored in the object pointed to by endptr, provided that
endptr is not a null pointer.
In other than the C or POSIX locale, additional locale-specific
subject sequence forms may be accepted.
If the subject sequence is empty or does not have the expected
form, no conversion is performed; the value of nptr shall be
stored in the object pointed to by endptr, provided that endptr
is not a null pointer.
These functions shall not change the setting of errno if
successful.
Since 0, {LONG_MIN} or {LLONG_MIN}, and {LONG_MAX} or {LLONG_MAX}
are returned on error and are also valid returns on success, an
application wishing to check for error situations should set
errno to 0, then call strtol() or strtoll(), then check errno.
Возвращаемое значение (Return value)
Upon successful completion, these functions shall return the
converted value, if any. If no conversion could be performed, 0
shall be returned and errno may be set to [EINVAL].
If the value of base is not supported, 0 shall be returned and
errno shall be set to [EINVAL].
If the correct value is outside the range of representable
values, {LONG_MIN}, {LONG_MAX}, {LLONG_MIN}, or {LLONG_MAX} shall
be returned (according to the sign of the value), and errno set
to [ERANGE].
Ошибки (Error)
These functions shall fail if:
EINVAL The value of base is not supported.
ERANGE The value to be returned is not representable.
These functions may fail if:
EINVAL No conversion could be performed.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
Since the value of *endptr is unspecified if the value of base is
not supported, applications should either ensure that base has a
supported value (0 or between 2 and 36) before the call, or check
for an [EINVAL] error before examining *endptr.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
fscanf(3p), isalpha(3p), strtod(3p)
The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)
