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STRTOU(3)                  Library Functions Manual                  STRTOU(3)

NAME
     strtou -- convert a string to an uintmax_t integer

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <inttypes.h>

     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' 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(3), 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.  OpenBSD introduced the
     strtonum(3) function for the same purpose, but the interface makes it
     impossible to properly differentiate illegal returns.

BUGS
     Ignores the current locale.

NetBSD 7.1.2                    April 30, 2015                    NetBSD 7.1.2