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strtol
[string to long]

    SYNOPSIS
    #include <stdlib.h>
    long strtol(const char *s, char ** ptr,int base);

    long _strtol_r(void *reent,
                    const char *s, char ** ptr,int base);

DESCRIPTION
The function, strtol, 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; it always includes 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 in . 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.

COMPLIANCE
strtol is ANSI.
No supporting OS subroutines are required.