STRTOUL(3) BSD Programmer's Manual STRTOUL(3)
strtoul, strtouq - convert a string to an unsigned long or uquad_t
strtoul(const char *nptr, char **endptr, int base);
strtouq(const char *nptr, char **endptr, int base);
The strtoul() function converts the string in nptr to an unsigned long
value. The strtouq() function converts the string in nptr 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 deter-
mined 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
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 charac-
ter 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 non nil, 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 nptr in *endptr. (Thus, if *nptr is not `\0'
but **endptr is `\0' on return, the entire string was valid.)
The strtoul() function returns either the result of the conversion or, if
there was a leading minus sign, the negation of the result of the conver-
sion, unless the original (non-negated) value would overflow; in the lat-
ter case, strtoul() returns ULONG_MAX and sets the global variable errno
[ERANGE] The given string was out of range; the value converted has been
The strtoul() function conforms to ANSI C X3.159-1989 (``ANSI C '').
Ignores the current locale.
4.4BSD June 4, 1993 1