NAME

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

SYNOPSIS

       #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)):

       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 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.

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 int
       value.

EXAMPLE

       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

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       information   about   reporting   bugs,   and   the  latest  version  of  this  page,  can  be  found  at
       https://www.kernel.org/doc/man-pages/.