STRTOUL(3) BSD Library Functions Manual STRTOUL(3)
strtoul, strtoull, strtoumax, strtouq -- convert a string to an unsigned long, unsigned long long, uintmax_t, or u_quad_t integer
Standard C Library (libc, -lc)
strtoul(const char *restrict str, char **restrict endptr, int base);
unsigned long long
strtoull(const char *restrict str, char **restrict endptr, int base);
strtoumax(const char *restrict str, char **restrict endptr, int base);
strtouq(const char *str, char **endptr, int base);
The strtoul() function converts the string in str to an unsigned long value. The strtoull() function converts the string in str to an
unsigned long long value. The strtoumax() function converts the string in str to an uintmax_t value. The strtouq() function converts the
string in str to a u_quad_t value. The conversion is done 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(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 an unsigned long value in the obvious manner, stopping at the end of the string or at the first
character that does not produce 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 not NULL, strtoul() stores the address of the first invalid character in *endptr. If there were no digits at all, however,
strtoul() stores the original value of str in *endptr. (Thus, if *str is not '