NAME

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

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <stdlib.h>

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

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

       strtoull():
           _ISOC99_SOURCE
               || /* glibc <= 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, and the base is supported, 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

       This function does not modify errno on success.

       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 │
       └────────────────────────────────────────────────────────┴───────────────┴────────────────┘

VERSIONS

       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().

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       strtoul()
              POSIX.1-2001, C89, SVr4.

       strtoull()
              POSIX.1-2001, C99.

CAVEATS

       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.

       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)