Originální popis anglicky:
strtol, strtoll - convert a string to a long integer
Návod, kniha: POSIX Programmer's Manual
#include <stdlib.h>
long strtol(const char *restrict
str, char
**restrict endptr, int
base );
long long strtoll(const char *restrict
str, char
**restrict endptr,
int
base)
These functions shall convert the initial portion of the string pointed to by
str 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 null byte 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 minus sign, 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 locales, other implementation-defined
subject sequences may be accepted.
If the subject sequence is empty or does not have the expected form, no
conversion is performed; the value of
str is stored in the object
pointed to by
endptr, provided that
endptr is not a null
pointer.
The
strtol() function 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.
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 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].
These functions shall fail if:
- ERANGE
- The value to be returned is not representable.
These functions may fail if:
- EINVAL
- The value of base is not supported.
The following sections are informative.
None.
None.
None.
None.
isalpha() ,
scanf() ,
strtod() , the Base Definitions
volume of IEEE Std 1003.1-2001,
<stdlib.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
