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


       #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

       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 attributes(7).

       │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

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

       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 strtoul().

       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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