strtoul

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



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():
           XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE
           || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

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
       upper or lower case 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() conforms to SVr4, C89, C99 and POSIX-2001, and strtoull() to
       C99 and POSIX.1-2001.

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

COLOPHON
       This page is part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can be
       found at http://www.kernel.org/doc/man-pages/.



GNU                                2011-09-15                         STRTOUL(3)