Converts strings of ASCII characters to the appropriate numeric
    values.

    Format

      #include  <stdlib.h>

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

1  –  Function Variants

    The strtol function has variants named _strtol32 and _strtol64
    for use with 32-bit and 64-bit pointer sizes, respectively.

2  –  Arguments

 nptr

    A pointer to the character string to be converted to a long.

 endptr

    The address of an object where the function can store a pointer
    to the first unrecognized character encountered in the conversion
    process (that is, the character that follows the last character
    in the string being converted). If endptr is a NULL pointer, the
    address of the first unrecognized character is not retained.

 base

    The value, 2 through 36, to use as the base for the conversion.

3  –  Description

    The strtol function recognizes strings in various formats,
    depending on the value of the base. This function ignores
    any leading white-space characters (as defined by isspace in
    <ctype.h>) in the given string. It recognizes an optional plus
    or minus sign, then a sequence of digits or letters that may
    represent an integer constant according to the value of the base.
    The first unrecognized character ends the conversion.

    Leading zeros after the optional sign are ignored, and 0x or 0X
    is ignored if the base is 16.

    If base is 0, the sequence of characters is interpreted by
    the same rules used to interpret an integer constant: after
    the optional sign, a leading 0 indicates octal conversion, a
    leading 0x or 0X indicates hexadecimal conversion, and any other
    combination of leading characters indicates decimal conversion.

    Truncation from long to int can take place after assignment or
    by an explicit cast (arithmetic exceptions not withstanding).
    The function call atol (str) is equivalent to strtol (str,
    (char**)NULL, 10).

4  –  Return Values

    x                  The converted value.
    LONG_MAX or LONG_  Indicates that the converted value would cause
    MIN                an overflow.
    0                  Indicates that the string starts with an
                       unrecognized character or that the value for
                       base is invalid. If the string starts with
                       an unrecognized character, *endptr is set to
                       nptr.