strtoul

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.1‐2017 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 '0' optionally followed by a
       sequence of the digits '0' to '7' 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(3P)