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



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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.1-2017
       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
       representation, 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 ''00'' optionally
       followed by a sequence of the digits ''00'' to ''77'' only. A hexadecimal
       constant 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
       subject sequence is a sequence of letters and digits representing an
       integer 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 <hyphen-minus>, 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,
       provided that endptr is not a null pointer.

       In other than the C or POSIX locale, additional locale-specific subject
       sequence forms 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
       strtoull(), 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.1-2017, <stdlib.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  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.opengroup.org/unix/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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                           STRTOUL(3)
