strtol---string to long
#include <stdlib.h>
long strtol(const char *s, char **ptr,int base);
long _strtol_r(void *reent,
const char *s, char **ptr,int base);
Descriptionstrtol converts the string *s to
a long. First, it breaks down the string into three parts:
leading whitespace, which is ignored; a subject string consisting
of characters resembling an integer in the radix specified by base;
and a trailing portion consisting of zero or more unparseable characters,
and always including the terminating null character. Then, it attempts
to convert the subject string into a long and returns the
result.
If the value of base is 0, the subject string is expected to look
like a normal C integer constant: an optional sign, a possible `0x'
indicating a hexadecimal base, and a number. If base is between
2 and 36, the expected form of the subject is a sequence of letters
and digits representing an integer in the radix specified by base,
with an optional plus or minus sign. The letters a--z (or,
equivalently, A--Z) are used to signify values from 10 to 35;
only letters whose ascribed values are less than base are
permitted. If base is 16, a leading 0x is permitted.
The subject sequence is the longest initial sequence of the input string that has the expected form, starting with the first non-whitespace character. If the string is empty or consists entirely of whitespace, or if the first non-whitespace character is not a permissible letter or digit, the subject string is empty.
If the subject string is acceptable, and the value of base is zero,
strtol attempts to determine the radix from the input string. A
string with a leading 0x is treated as a hexadecimal value; a string with
a leading 0 and no x is treated as octal; all other strings are
treated as decimal. If base is between 2 and 36, it is used as the
conversion radix, as described above. If the subject string begins with
a minus sign, the value is negated. Finally, a pointer to the first
character past the converted subject string is stored in ptr, if
ptr is not NULL.
If the subject string is empty (or not in acceptable form), no conversion
is performed and the value of s is stored in ptr (if ptr is
not NULL).
The alternate function _strtol_r is a reentrant version. The
extra argument reent is a pointer to a reentrancy structure.
Returns
strtol returns the converted value, if any. If no conversion was
made, 0 is returned.
strtol returns LONG_MAX or LONG_MIN if the magnitude of
the converted value is too large, and sets errno to ERANGE.
Portability
strtol is ANSI.
No supporting OS subroutines are required.