STRTOUL(3)              NetBSD Library Functions Manual             STRTOUL(3)

NAME
     strtou, strtoul, strtoull, strtoumax, strtouq -- convert a string to an
     unsigned long, unsigned long long, uintmax_t or uquad_t integer

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdlib.h>
     #include <limits.h>

     unsigned long int
     strtoul(const char * restrict nptr, char ** restrict endptr, int base);

     unsigned long long int
     strtoull(const char * restrict nptr, char ** restrict endptr, int base);

     #include <inttypes.h>

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

     uintmax_t
     strtoumax(const char * restrict nptr, char ** restrict endptr, int base);

     #include <sys/types.h>
     #include <stdlib.h>
     #include <limits.h>

     u_quad_t
     strtouq(const char * restrict nptr, char ** restrict endptr, int base);

DESCRIPTION
     The strtoul() function converts the string in nptr to an unsigned long
     int value.  The strtoull() function converts the string in nptr to an
     unsigned long long int value.  The strtoumax() function converts the
     string in nptr to an uintmax_t value.  strtou() function uses internally
     strtoumax() 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 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
     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 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.)

RETURN VALUES
     The strtou() function always returns the closest value in the range spec-
     ified by the lo and hi arguments.  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 conversion, unless the original (non-
     negated) value would overflow; in the latter case, strtoul() returns
     ULONG_MAX, strtoull() returns ULLONG_MAX, strtoumax() returns
     UINTMAX_MAX, strtouq() returns UQUAD_MAX, and the global variable errno
     is set to ERANGE.

     There is no way to determine if strtoul() has processed a negative number
     (and returned an unsigned value) short of examining the string in nptr
     directly.  If the base argument is not supported then errno is set to
     EINVAL and the functions return 0.

     If no error occurs, errno is left unchanged.  This behavior (which is
     unlike most library functions) is guaranteed by the pertinent standards.

EXAMPLES
     The strtou() function is the simplest to use:

           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);

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

     Because the return value of strtoul() cannot be used unambiguously to
     detect an error, errno is left unchanged after a successful call.  To
     ensure that a string is a valid number (i.e., in range and containing no
     trailing characters), clear errno beforehand explicitly, then check it
     afterwards:

           char *ep;
           unsigned long ulval;

           ...

           errno = 0;
           ulval = strtoul(buf, &ep, 10);
           if (buf[0] == '\0' || *ep != '\0')
                   goto not_a_number;
           if (errno == ERANGE && ulval == ULONG_MAX)
                   goto out_of_range;

     This example will accept ``12'' but not ``12foo'' or ``12\n''.  If trail-
     ing whitespace is acceptable, further checks must be done on *ep; alter-
     nately, use sscanf(3).

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

     [ERANGE]           The given string was out of range; the value converted
                        has been clamped.

     In addition to the above errors strtou() returns:

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

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

     [ERANGE]           The range given was invalid, i.e.  lo > hi.

SEE ALSO
     strtoi(3), strtoimax(3), strtol(3), strtoll(3)

STANDARDS
     The strtoul() function conforms to ANSI X3.159-1989 (``ANSI C89'').  The
     strtoull() and strtoumax() functions conform to ISO/IEC 9899:1999
     (``ISO C99'').  The strtou() function appeared in NetBSD 8.

BUGS
     Ignores the current locale.

NetBSD 7.0                      March 10, 2015                      NetBSD 7.0

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