NAME

     strtou — convert a string to an uintmax_t integer

LIBRARY

     Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS

     #include <inttypes.h>
     (See libbsd(7) for include usage.)

     uintmax_t
     strtou(const char * restrict nptr, char ** restrict endptr, int base, uintmax_t lo,
         uintmax_t hi, int *rstatus);

DESCRIPTION

     The strtou() function converts the string in nptr to an uintmax_t value.  The strtou()
     function uses internally strtoumax(3) and ensures that the result is always in the range [
     lo .. hi ].  In adddition it always places 0 on success or a conversion status in the
     rstatus argument, avoiding the errno gymnastics the other functions require.  The rstatus
     argument can be NULL if conversion status is to be ignored.

     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’ or ‘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 uintmax_t 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 non-nil, strtou() stores the address of the first invalid character in *endptr.
     If there were no digits at all, however, strtou() 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.)

RETURN VALUES

     The strtou() function always returns the closest value in the range specified by the lo and
     hi arguments.

     The errno value is guaranteed to be left unchanged.

     Errors are stored as the conversion status in the rstatus argument.

EXAMPLES

     The following example will always return a number in [1..99] range no matter what the input
     is, and warn if the conversion failed.

           int e;
           uintmax_t lval = strtou(buf, NULL, 0, 1, 99, &e);
           if (e)
                   warnc(e, "conversion of `%s' to a number failed, using %ju",
                       buf, lval);

ERRORS

     [ECANCELED]        The string did not contain any characters that were converted.

     [EINVAL]           The base is not between 2 and 36 and does not contain the special value
                        0.

     [ENOTSUP]          The string contained non-numeric characters that did not get converted.
                        In this case, endptr points to the first unconverted character.

     [ERANGE]           The given string was out of range; the value converted has been clamped;
                        or the range given was invalid, i.e.  lo > hi.

SEE ALSO

     atof(3), atoi(3), atol(3), atoll(3), strtod(3), strtoi(3bsd), strtoimax(3), strtol(3),
     strtoll(3), strtoul(3), strtoull(3), strtoumax(3)

STANDARDS

     The strtou() function is a NetBSD extension.

HISTORY

     The strtou() function first appeared in NetBSD 7.0.  OpenBSD introduced the strtonum(3bsd)
     function for the same purpose, but the interface makes it impossible to properly
     differentiate illegal returns.

BUGS

     Ignores the current locale.