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       strtoul,  strtoull,  strtouq  -  convert  a  string to an unsigned long


       #include <stdlib.h>

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

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

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           _XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE ||
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99


       The  strtoul() function converts the initial part of the string in nptr
       to an unsigned long int value 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
       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 unsigned long int  value
       in  the  obvious manner, stopping at the first character which is not a
       valid digit in the given base.  (In bases above 10, the letter  'A'  in
       either  uppercase or lowercase represents 10, 'B' represents 11, and so
       forth, with 'Z' representing 35.)

       If endptr is not NULL,  strtoul()  stores  the  address  of  the  first
       invalid  character  in  *endptr.   If  there  were  no  digits  at all,
       strtoul() stores the original value of nptr in *endptr (and returns 0).
       In particular, if *nptr is not '\0' but **endptr is '\0' on return, the
       entire string is valid.

       The strtoull() function works just  like  the  strtoul()  function  but
       returns an unsigned long long int value.


       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  represented  as  an  unsigned  value,  unless  the original
       (nonnegated) value  would  overflow;  in  the  latter  case,  strtoul()
       returns  ULONG_MAX  and sets errno to ERANGE.  Precisely the same holds
       for strtoull() (with ULLONG_MAX instead of ULONG_MAX).


       EINVAL (not in C99) The given base contains an unsupported value.

       ERANGE The resulting value was out of range.

       The implementation may also set errno to EINVAL in case  no  conversion
       was performed (no digits seen, and 0 returned).


       For   an   explanation   of   the  terms  used  in  this  section,  see

       │InterfaceAttributeValue          │
       │strtoul(), strtoull(), strtouq() │ Thread safety │ MT-Safe locale │


       strtoul(): POSIX.1-2001, POSIX.1-2008, C89, C99 SVr4.

       strtoull(): POSIX.1-2001, POSIX.1-2008, C99.


       Since strtoul() can legitimately return 0 or ULONG_MAX (ULLONG_MAX  for
       strtoull()) on both success and failure, the calling program should set
       errno to 0 before the call, and then determine if an error occurred  by
       checking whether errno has a nonzero value after the call.

       In  locales  other  than the "C" locale, other strings may be accepted.
       (For example, the thousands separator of  the  current  locale  may  be

       BSD also has

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

       with completely analogous definition.  Depending on the wordsize of the
       current architecture, this  may  be  equivalent  to  strtoull()  or  to

       Negative  values  are considered valid input and are silently converted
       to the equivalent unsigned long int value.


       See the example on the strtol(3) manual page; the use of the  functions
       described in this manual page is similar.


       atof(3), atoi(3), atol(3), strtod(3), strtol(3)


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