NAME

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

SYNOPSIS

       #include <stdlib.h>

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

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

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

       strtoull():
           _ISOC99_SOURCE ||
               || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE

DESCRIPTION

       The  strtoul()  function  converts  the  initial  part  of  the  string in nptr to an unsigned long 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 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 value.

RETURN 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).

ERRORS

       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).

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).
       ┌──────────────────────────────────┬───────────────┬────────────────┐
       │ Interface                        │ Attribute     │ Value          │
       ├──────────────────────────────────┼───────────────┼────────────────┤
       │ strtoul(), strtoull(), strtouq() │ Thread safety │ MT-Safe locale │
       └──────────────────────────────────┴───────────────┴────────────────┘

CONFORMING TO

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

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

NOTES

       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 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
       value.

EXAMPLES

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

SEE ALSO

       a64l(3), atof(3), atoi(3), atol(3), strtod(3), strtol(3), strtoumax(3)

COLOPHON

       This page is part of release 5.10 of  the  Linux  man-pages  project.   A  description  of  the  project,
       information   about   reporting   bugs,   and   the  latest  version  of  this  page,  can  be  found  at
       https://www.kernel.org/doc/man-pages/.

GNU                                                2020-11-01                                         STRTOUL(3)