strtol - convert a string to a long integer

#include <stdlib.h>
#include <limits.h>

long strtol(const char *nptr, char **endptr, int base);

Strtol converts the string in nptr to a long value according to the
given base, which must be between 2 and 36 inclusive, or be the
special value 0.

The string may begin with an arbitrary amount of white space (as
determined by isspace; see ctype(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 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 non nil, strtol stores the address of the first
invalid character in *endptr. If there were no digits at all,
however, strtol stores the original value of nptr in *endptr.
(Thus, if *nptr is not ’ ’ but **endptr is ’ ’ on return, the
entire string was valid.)

Strtol 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.

The given string was out of range; the value converted has
been clamped.

atof(3), atoi(3), atol(3), strtod(3), strtoul(3)

Strtol conforms to ANSI X3.159-1989 ("ANSI C").

Ignores the current locale.