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

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 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 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(): POSIX.1-2001, POSIX.1-2008, C89, C99 SVr4.

   strtoull(): POSIX.1-2001, POSIX.1-2008, C99.

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

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

COLOPHON

   This page is part of release 4.09 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
   https://www.kernel.org/doc/man-pages/.

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