strtoul(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       strtoul, strtoull — convert a string to an unsigned long

SYNOPSIS         top

       #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         top

       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         top

       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         top

       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         top

       None.

APPLICATION USAGE         top

       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         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       fscanf(3p), isalpha(3p), strtod(3p), strtol(3p)

       The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)

COPYRIGHT         top

       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)

Pages that refer to this page: stdlib.h(0p)a64l(3p)fscanf(3p)strtoimax(3p)