NAME

       strtou — convert a string value 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 addition 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 which is not 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.

       The range check is more important than the unconverted characters check, and it is performed first.  If a
       program needs to know if there were unconverted characters when an out of range number has been provided,
       it needs to supply and test endptr.

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.

Debian                                          January 20, 2024                                    strtou(3bsd)