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


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


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


     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 deter-
     mined 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,  str-
     toul()  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.


     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  (non-
     negated)  value  would  overflow; in the latter case, strtoul() returns
     ULONG_MAX and sets errno to ERANGE.  Precisely the same holds for  str-
     toull() (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
     |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 sup-
     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  str-
     Negative  values  are considered valid input and are silently converted
     to the equivalent unsigned long int 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)


     This  page  is  part of release 4.16 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 2017-09-15 STRTOUL(3)

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