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STRTOUL(3P)                POSIX Programmer's Manual               STRTOUL(3P)
PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       strtoul, strtoull -- convert a string to an unsigned long
SYNOPSIS
       #include <stdlib.h>
       unsigned long strtoul(const char *restrict str,
           char **restrict endptr, int base);
       unsigned long long strtoull(const char *restrict str,
           char **restrict endptr, int base);
DESCRIPTION
       The functionality described on this reference page is aligned with  the
       ISO C  standard.  Any  conflict between the requirements described here
       and the ISO C standard is unintentional. This  volume  of  POSIX.1-2008
       defers to the ISO C standard.
       These functions shall convert the initial portion of the string pointed
       to by str to a type unsigned long and unsigned  long  long  representa-
       tion,  respectively.  First, they decompose the input string into three
       parts:
        1. An initial, possibly empty, sequence of white-space characters  (as
           specified by isspace())
        2. A  subject  sequence  interpreted as an integer represented in some
           radix determined by the value of base
        3. A final string of one or more  unrecognized  characters,  including
           the terminating NUL character of the input string
       Then  they shall attempt to convert the subject sequence to an unsigned
       integer, and return the result.
       If the value of base is 0, the expected form of the subject sequence is
       that  of  a  decimal constant, octal constant, or hexadecimal constant,
       any of which may be preceded by a '+' or '-' sign. A  decimal  constant
       begins  with  a  non-zero  digit, and consists of a sequence of decimal
       digits. An octal constant consists of the prefix  '0'  optionally  fol-
       lowed  by  a sequence of the digits '0' to '7' only. A hexadecimal con-
       stant consists of the prefix 0x or 0X followed by  a  sequence  of  the
       decimal  digits and letters 'a' (or 'A') to 'f' (or 'F') with values 10
       to 15 respectively.
       If the value of base is between 2 and 36, the expected form of the sub-
       ject sequence is a sequence of letters and digits representing an inte-
       ger with the radix specified by base, optionally preceded by a  '+'  or
       '-'  sign.  The letters from 'a' (or 'A') to 'z' (or 'Z') inclusive are
       ascribed the values 10 to 35; only letters whose  ascribed  values  are
       less  than  that of base are permitted. If the value of base is 16, the
       characters 0x or 0X may optionally precede the sequence of letters  and
       digits, following the sign if present.
       The  subject  sequence is defined as the longest initial subsequence of
       the input string, starting with  the  first  non-white-space  character
       that  is  of  the  expected form. The subject sequence shall contain no
       characters if the input string is empty or consists entirely of  white-
       space  characters,  or  if the first non-white-space character is other
       than a sign or a permissible letter or digit.
       If the subject sequence has the expected form and the value of base  is
       0,  the  sequence  of characters starting with the first digit shall be
       interpreted as an integer constant. If the  subject  sequence  has  the
       expected  form  and  the value of base is between 2 and 36, it shall be
       used as the base for conversion, ascribing to each letter its value  as
       given  above.  If  the  subject  sequence begins with a minus-sign, the
       value resulting from the conversion shall be negated. A pointer to  the
       final  string  shall be stored in the object pointed to by endptr, pro-
       vided that endptr is not a null pointer.
       In other than the C or POSIX locales, other implementation-defined sub-
       ject sequences may be accepted.
       If the subject sequence is empty or does not have the expected form, no
       conversion shall be performed; the value of str shall be stored in  the
       object  pointed  to  by  endptr,  provided  that  endptr  is not a null
       pointer.
       These functions shall not change the setting of errno if successful.
       Since 0, {ULONG_MAX}, and {ULLONG_MAX} are returned on  error  and  are
       also  valid  returns  on  success,  an application wishing to check for
       error situations should set errno to 0, then  call  strtoul()  or  str-
       toull(), then check errno.
RETURN VALUE
       Upon  successful completion, these functions shall return the converted
       value, if any. If no conversion could be performed, 0 shall be returned
       and errno may be set to [EINVAL].
       If  the  value  of base is not supported, 0 shall be returned and errno
       shall be set to [EINVAL].
       If the correct value is outside  the  range  of  representable  values,
       {ULONG_MAX}  or  {ULLONG_MAX}  shall  be  returned  and  errno  set  to
       [ERANGE].
ERRORS
       These functions shall fail if:
       EINVAL The value of base is not supported.
       ERANGE The value to be returned is not representable.
       These functions may fail if:
       EINVAL No conversion could be performed.
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       Since the value of *endptr is unspecified if the value of base  is  not
       supported,  applications should either ensure that base has a supported
       value (0 or between 2 and 36) before the call, or check for an [EINVAL]
       error before examining *endptr.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       fscanf(), isalpha(), strtod(), strtol()
       The Base Definitions volume of POSIX.1-2008, <stdlib.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the  referee document. The original Standard can be obtained online
       at http://www.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                          STRTOUL(3P)