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 man‐
       ner,  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'  repre‐
       sents 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  str‐
       toull() (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
   Multithreading (see pthreads(7))
       The strtoul(), strtoull(), and strtouq() functions are thread-safe with exceptions.  These
       functions can be safely used in multithreaded applications, as long as setlocale(3) is not
       called to change the locale during their execution.

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 architec‐
       ture, 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 3.74 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 http://www.kernel.org/doc/man-pages/.



GNU                                         2014-03-18                                 STRTOUL(3)