STRTOUL(3)                  Linux Programmer's Manual                 STRTOUL(3)

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

       #include <stdlib.h>

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

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

               || /* Glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE

       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

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

       │Interface                              Attribute     Value          │
       │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 value.

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

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

       This page is part of release 5.13 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

GNU                                2021-03-22                         STRTOUL(3)