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XXCOPY TECHNICAL BULLETIN #17
From: Kan Yabumoto email@example.com
To: XXCOPY user
Subject: Selecting files by file date amd time using XXCOPY
Date: 2001-02-23 (revised)
The filedate value offers yet another trait to select files for
various file management operations. Microsoft's XCOPY allows you
to specify a cut-off date to select some recently created files.
Our XXCOPY, on the other hand, seizes the opportunity with respect
to the filedate (and time) to a much greater extent for qualifying
files for a large collection of functions.
While the fundamental elements of filedate-related operations are
quite simple, the total number of variations may be daunting
to some users. So to ease the pain of memorizing the details,
here in this article, simpler things are presented first, followed
by more complicated aspects.
The file date/time related XXCOPY switches.
The ten basic filetime switches fall into either of the two groups:
Comparison to the reference file (newer/older/same/different)
/DA, /DB, /DS, /DX ; newer, older, same, different
Relative and Absolute date specifiers (you give the range of date)
/DA#n, /DB#n, /DO#n ; as how many days ago from today
/DA:date, /DB:date, /DO:date ; date specified as yyyy-mm-dd
Comparing the filetime of two files
The filetime comparison switches are used mainly for directory
synchronization and various backup operations based on file time.
Therefore, in all cases, the file time comparison is made on a
pair of files; one from the first (source) directory, and the other
from the second (destination ,or sometimes reference) directory.
In this case, the pair of files are compared not only by the
filedate, but also by the file time to the finest value (hour,
minute, and second) (see below for /FF for details). Since the
comparison is made on the file time value which are stored in
the respective directory, the XXCOPY user does not specify the
value and therefore, the command syntax for these switches are
the simplest; /D, /DA, /DB, /DX, /DS without any user-specified
/D Same as /DA
/DA Copies newer files and brand new files.
/DB Copies older files and brand new files.
/DX Copies different-date files only.
/DS Copies same date/time files only.
Testing file's date against a user-specified date range
Unlike the file time comparison method presented in the preceding
section, XXCOPY allows you to select files based on the filedate
associated with each file which are expressed in either the relative
date (how many days ago from today), or the absolute date (specified
in year, month and day). For this feature, XXCOPY maintains one
or two dates to qualify files for file management operations.
"A-date value" for On-or-After date (entered by /DA: or /DA#)
"B-date value" for On-or-Before date (entered by /DB: or /DA#)
The relative date specifiers
System administrators often refer to a group of files by the age
of the files for backup operations. One of the most natural ways
of specifying them is the file age measured in days (relative to
the current date).
/DA#<n> Copies files that were changed on or after <n> days ago.
/DB#<n> Copies files that were changed on or before <n> days ago.
Examples of command lines using the relative date:
XXCOPY src dst /DA#60 // After 60 days ago
XXCOPY src dst /DB#30 // Before 30 days ago
XXCOPY src dst /DA#60 /DB#30 // files with age of 30-60 days
XXCOPY src dst /D#100 // same as /DA#100
As you can see from the examples, you may specify only one of
the "A-date value" and "B-date value" or both. If you specify
only one date value, then the other end is open-ended.
Note that the file age is measured by the number of days starting
0 (zero) as the value for files made today, 1 (one) for files made
yesterday, and so on.
When you specify both the "A-date value" and "B-date value", the
date range you specify may be used for an inclusive selection or
exclusive selection, depending on which of the two values are newer.
The following examples illustrate this point more clearly.
XXCOPY src dst /DA#60 /DB#30 // files with age of 30-60 days
XXCOPY src dst /DB#60 /DA#30 // age >= 60 or age <= 30
Here, two same date values are specified for the opposite
/DA: and /DB: switches. The first example is the most common
case where the two dates specify the beginning and the end of
a single period. On the other hand, the second example shows
different case where the two date are applied toward the
opposite direction in the timeline which in effect excludes
files in the excluded period (files with age 31-59 days are
NOT selected) --- such a case is accepted as a valid command.
Note that when the age is referred to by the number of days,
it is not measured by the multiple of 24 hours. Rather, the 0th day
(today) began at midnight today to take care any fraction of today.
That is, /DA#0 specifies the files made on or after midnight today.
This scheme allows the cut-off time to be midnight of each day.
The relative time specifiers
The relative time specifier adds few more twists to the relative
date specifier. In the /DA#n /DB#n or /DO#n switches, when the
age value n is given as a number without a suffix, the age will
be measured by number of the days. This is probably most common
usage. But, you may add a single-letter suffix (D, H, M, or S)
to the value (for Days, Hours, Minutes or Seconds, respectively).
XXCOPY src /S /LDT /DA#30M // list files made within 30 min.
XXCOPY src dst /s /DA#24H // copy files made within 24 hours
XXCOPY src dst /s /DA#0 // copy files made today (since midnight)
The absolute date specifiers
Since we reference dates by year, month and day quite often in
our day-to-day lives, it is also very natural for us to specify
the file time as such.
/DA:<date> Copies files that were changed on or after the specified date.
/DB:<date> Copies files that were changed on or before the specified date.
Examples of command lines using the absolute date:
XXCOPY src dst /DA:2000-1-1
XXCOPY src dst /DB:1999-12-31
XXCOPY src dst /DA:1998-1-1 /DB:2000-8-31
XXCOPY src dst /D:1998-1-1 // same as /DA#1998-1-1
Now, you already know the essential mechanism of XXCOPY which controls
file selection based on the filedate. Nearly all of the remaining
discussion is for various shortcuts and clarifications of details.
The "O-date value" for the same parameter
When the "A-date value" is the same as the "B-date value" (to specify
a particular date), you may use the third way, the "O-date value" to
combine the two into one parameter.
You can use the "O-date value" (On the date) whenever the "A-date value"
and the "B-date value" are the same. (Here, the letter O (oh, not zero)
is shown in lowercase (o) to avoid confusion.)
The following two commands are equivalent:
XXCOPY src dst /DA:2000-5-1 /DB:2000-5-1
XXCOPY src dst /Do:2000-5-1
It also applies to the relative date specifier. The following
two commands are equivalent.
XXCOPY src dst /DA#80 /DB#80
XXCOPY src dst /Do#80
Shortcut for Today and Yesterday
One of the most common date used with XXCOPY is the current date
(today) and one day earlier (yesterday). So, we assign the dot (.)
parameter as a shortcut for today's date for the /DA and /Do switches,
and as a shortcut for yesterday's date for the /DB switch.
/DB:. or /DB#. specify filedate date is Yesterday or earlier.
/DA:. or /DA#. specify filedate that is today or later.
/Do:. or /Do#. specify filedate that is today only.
Partial date specifiers
You may specify a month by omitting the day-of-the-month value. If
only two numbers are given, one must be a 4-digit year value. The
following command lines all specify the entire month of February, 2000.
The "B-date value" in this context specifies the last day of the
month, and the "O-date value" in this context specify the whole month.
XXCOPY src dst /DA:2000-2-1 /DB:2000-2-29
XXCOPY src dst /DA:2000-2 /DB:2000-2
XXCOPY src dst /Do:2000-2
Similarly, you may specify the filedate by the year.
The following three cases are equivalent.
XXCOPY src dst /DA:2000-1-1 /DB:2000-12-31
XXCOPY src dst /DA:2000 /DB:2000
XXCOPY src dst /Do:2000
The partial date specifiers that are shown so far are for the cases
of the whole month and the whole year. But, the usage of partial date
specifier is not limited to such cases. When it is used for the
/DA parameter, the partial date value specifies the first day of
the month/year. When it is used for the /DB parameter, it denotes
the end of the month/year. And, when it is used for the /Do
parameter, it selects the whole month/year. Here are some examples.
XXCOPY src dst /DA:1999-4 // same as /DA:1999-04-01
XXCOPY src dst /DA:1998 // same as /DB:1998-01-01
XXCOPY src dst /DB:2000-5 // same as /DB:2000-05-31
XXCOPY src dst /DB:1998 // same as /DB:1998-12-31
XXCOPY src dst /Do:2000-2 // the month of Feb, 2000
XXCOPY src dst /Do:2000 // the whole year 2000
XXCOPY src dst /DA:1998-4 /DB:1999 // /DA:1998-04-01 /DB:1999-12-31
The relative and absolute date specifiers can be mixed in a command.
Although most users avoid mixing the two types of expressing the
date value, there is nothing inherently wrong about using both the
relative and absolute date specifiers.
XXCOPY src dst /DA:2000-1-1 /DB#7
This example specifies files that are at least one week old
which are made in the year 2000.
You cannot specify two periods in timeline in one XXCOPY command.
That is, XXCOPY maintains one "A-date value" and one "B-date value".
If you specify two A-date values, the first such value will be
We endorse the ISO-8601 convention (DMXXTB #025) which denotes the date/time value in
the most logical order. But, XXCOPY also accepts other conventions
if the date value is unambiguously specified. It allows one of the
three (ISO, US and EU) conventions to be used for an absolute date
specifier as long as it is value is unambiguous. For example,
/DA:2000-01-02 // ISO the first value is larger than 1970
/DA:0-1-2 // ISO 0 (for 2000) cannot be for month or day
/DA:12-13-2000 // US the value 13 cannot be a month value
/DA:01-13-01 // US the only one to have 13 in the middle
/DA:13-10-2000 // EU the value 13 cannot be a month value
This applies to the partial date specifiers. Therefore, both
/DA:2000-03 and /DA:03-2000 are accepted as equally unambiguous.
But, when there are more than one way to interpret the date value,
the system's date format setting will be used to resolve ambiguity.
The following date specifiers are such ambiguous cases and we
suggest you avoid these cases.
/DA:1-2-3 // can be ISO, US, or EU; pretty bad
/DA:12-12-12 // can be ISO, US, or EU
/DA:1-2-2000 // can be US or EU
/DA:11-12-13 // can be ISO, US, or EU
/DA:13-12-11 // can be ISO, or EU
I hope by now, you are convinced of the superiority of the ISO
notation which also gives you the convenience of easy sorting.
In the case of the partial date specifier, the year value must
always be in a full 4-digit value. In this case, the order of
the year and month value can be switched without causing any
ambiguity. For example;
/DA:2000-01 // partial ISO notation
/DA:12-1999 // US/EU
File time-related switches
All file time related functions can be further modified by various
switches to meet your specific needs which may be different from
the majority users.
/FW, /FA, /FC (Last-Written, Last-Accessed, Created)
Under normal circumstances, the file date/time XXCOPY uses is the
time the file was last written (the commonly used file time value,
/FW as the default), it can be substituted by the last-accessed
time (/FA) or file creation time (/FC).
/FL, /FU (Local time, UTC time)
The commonly used file time is expressed by the local time (/FL
as the default). However, in networking environment, it may be
more convenient for some users to enter the file time using the
UTC time (/FU) which is also known as GMT (Greenwich Mean Time).
/FF (Fuzzy Filetime)
When file time is compared against one another in a mixed OS
environment, the granularity of the file time stamp (which is
usually set by the particular file system) may cause problems.
For example, the FAT based file systems (FAT12, FAT16, FAT32)
uses file time which is measured by two second interval whereas
unix-based file system uses one second interval. The NTFS uses
much finer filetime. The /FF switch forces XXCOPY to ignore
the filetime difference within plus/minus 2 seconds so that
a timestamp-based incremental backup between an NTFS volume and
a FAT volume (or more broadly beteen different file systems)
without selecting all files due to the inherent difference in
the timestamp granularity.
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