How do I compare timestamps of files in a DOS batc

问题:

In DOS batch files, the method of achieving certain things is somewhat obfuscated. Fortunately, there is a fantastic reference site for DOS batch scripting: Simon Sheppard's SS64. (The same site also has plenty of information about Bash.)

One difficulty is branching execution based on whether a directory is empty. The obvious if exist "%dir%\*.*" doesn't work. But it can be done with this conditional execution trick:

( dir /b /a "%dir%" | findstr . ) > nul && (
  echo %dir% non-empty
) || (
  echo %dir% empty
)

Another awkward problem is branching according to file contents. Again that can be done like this:

( fc /B "%file1%" "%file2%" | find "FC: no differences encountered" ) > nul && (
  echo "%file1%" and "%file2%" are the same
) || (
  echo "%file1%" and "%file2%" are different
)

So, my question is:
Is there a way to do branch according to the time-stamps of files?

This is the sort of thing I want:

REM *** pseudo-code!
if "%file1%" is_newer_than "%file2%" (
  echo "%file1%" is newer
) else if "%file1%" is_older_than "%file2%" (
  echo "%file2%" is newer
) else (
  echo "%file1%" and "%file2%" are the same age
)

Thanks.

回答1:

You can find the newer of two files with one line of batch script. Just list the files in date order, oldest first, which means the last file listed must be the newer file. So if you save the file name each time, the last name put in your variable will be the newest file.

For, example:

SET FILE1=foo.txt
SET FILE2=bar.txt
FOR /F %%i IN ('DIR /B /O:D %FILE1% %FILE2%') DO SET NEWEST=%%i
ECHO %NEWEST% is (probably) newer.

This unfortunately doesn't cope with the date stamps being the same. So we just need to check if the files have the same date and time stamp first:

SET FILE1=foo.txt
SET FILE2=bar.txt

FOR %%i IN (%FILE1%) DO SET DATE1=%%~ti
FOR %%i IN (%FILE2%) DO SET DATE2=%%~ti
IF "%DATE1%"=="%DATE2%" ECHO Files have same age && GOTO END

FOR /F %%i IN ('DIR /B /O:D %FILE1% %FILE2%') DO SET NEWEST=%%i
ECHO Newer file is %NEWEST%

:END

回答2:

Dave Webb's soution while a great one will of course only work on files in the same directory.

Here is a solution that will work on any two files.

First get the file time (see How to get file's last modified date on Windows command line?).

for %%a in (MyFile1.txt) do set File1Date=%%~ta
for %%a in (MyFile2.txt) do set File2Date=%%~ta 

However one has then to manually break the date and time into it's components since Cmd.exe will compare them as a sting thus 2 > 10 and 10:00AM > 2:00PM.

Compare first the years, then the months, then the day, then AM/PM, then the hour, and then the minute and second, (actually time consuming, but I don't have on the minute a better idea), see the final code at the end.

However this solution will not work if the files are in the same minute but different by the second.

If you are to this level of precision then get the filetime by using the "forfiles" command (see https://superuser.com/questions/91287/windows-7-file-properties-date-modified-how-do-you-show-seconds).

for /F "tokens=*" %%a in ('forfiles /m MyFile1.txt /c "cmd /c echo @fdate @ftime"') 
    do set File1Date=%%a
for /F "tokens=*" %%a in ('forfiles /m MyFile2.txt /c "cmd /c echo @fdate @ftime"') 
    do set File2Date=%%a    

Note that "ForFiles" has a limitation that it can't take a path with spaces, so if you have a path with spaces you will have to change to that directory first, see forfiles - spaces in folder path

Comparison Code

:compareFileTime
set "originalFileTime=%1"
set "secondFileTime=%2"

for /F "tokens=1,2,3 delims= " %%a in (%originalFileTime%) do ( 
    set "originalDatePart=%%a"  
    set "originalTimePart=%%b"  
    set "originalAmPmPart=%%c"  
)
for /F "tokens=1,2,3 delims= " %%a in (%secondFileTime%) do (
    set "secondDatePart=%%a"
    set "secondTimePart=%%b"
    set "secondAmPmPart=%%c"
)
for /F "tokens=1,2,3 delims=/" %%a in ("%originalDatePart%") do (
        set "originalMonthPart=%%a"
        set "originalMonthDayPart=%%b"
        set "originalYearPart=%%c"

        rem We need to ensure that the year is in a 4 digit format and if not we add 2000 to it
        rem Cmd considers "50" > "100" but 50 < 100, so don't surround it with qoutes
    if %%c LSS 100 set "originalYearPart=20%%c
)
for /F "tokens=1,2,3 delims=/" %%a in ("%secondDatePart%") do (
    set "secondMonthPart=%%a"
    set "secondMonthDayPart=%%b"
    set "secondYearPart=%%c"    

    rem We need to ensure that the year is in a 4 digit format and if not we add 2000 to it
    rem Cmd considers "50" > "100" but 50 < 100, so don't surround it with quotes
        if %%c LSS 100 set "secondYearPart=20%%c    
)

if %originalYearPart% GTR %secondYearPart% goto newer
if %originalYearPart% LSS %secondYearPart% goto older

rem We reach here only if the year is identical
rem Cmd considers "2" > "10" but 2 < 10, so don't surround it with quotes or you will have to set the width explicitly
if %originalMonthPart% GTR %secondMonthPart% goto newer
if %originalMonthPart% LSS %secondMonthPart% goto older

if %originalMonthDayPart% GTR %secondMonthDayPart% goto newer
if %originalMonthDayPart% LSS %secondMonthDayPart% goto older

rem We reach here only if it is the same date
if %originalAmPmPart% GTR %secondAmPmPart% goto newer
if %originalAmPmPart% LSS %secondAmPmPart% goto older

rem we reach here only if i=t is the same date, and also the same AM/PM
for /F "tokens=1 delims=:" %%a in ("%originalTimePart%") do set "originalHourPart=%%a"

for /F "tokens=1 delims=:" %%a in ("%secondTimePart%") do set "secondHourPart=%%a"

rem Cmd considers "2" > "10" but 2 < 10, so don't surround it with qoutes or you will have to set the width explicitly
if %originalHourPart% GTR %secondHourPart% goto newer
if %originalHourPart% LSS %secondHourPart% goto older

rem The minutes and seconds can be compared directly
if %originalTimePart% GTR %secondTimePart% goto newer
if %originalTimePart% LSS %secondTimePart% goto older
if %originalTimePart% EQU %secondTimePart% goto same

goto older
exit /b

:newer
echo "newer"
exit /b

:older
echo "older"
exit /b

:same
echo "same"
exit /b

回答3:

seriously, you should start to learn something else. Its not a joke. DOS(cmd.exe) seriously lacks date manipulation capabilities and many more deficiencies. Here's the next better alternative natively provided besides DOS batch, vbscript

Set objFS = CreateObject("Scripting.FileSystemObject")
Set objArgs = WScript.Arguments
strFile1 = objArgs(0)
strFile2 = objArgs(1)
Set objFile1 = objFS.GetFile(strFile1)
Set objFile2 = objFS.GetFile(strFile2)
If objFile1.DateLastModified < objFile2.DateLastModified Then
    WScript.Echo "File1: "&strFile1&" is older than "&strFile2
Else
    WScript.Echo "File1: "&strFile1&" is newer than "&strFile2
End If 

run it on command line

C:\test>dir
 Volume in drive C has no label.
 Volume Serial Number is 08AC-4F03

 Directory of C:\test

11/06/2009  07:40 PM    <DIR>          .
11/06/2009  07:40 PM    <DIR>          ..
11/06/2009  06:26 PM               135 file
11/02/2009  04:31 PM             4,516 m.txt

C:\test>cscript /nologo test.vbs file m.txt
File1: file is newer than m.txt

Of course, in newer versions of windows, you may want to try out Powershell...

回答4:

Here's an easier solution. By concatenating the date parts as a single string from most significant to least significant, we can just do a simple string compare on the result.

In other words, comparing YYYYMMDDAMPMHHMM values will give the desired result without having to individually compare each segment of the date. This value is obtained by concatenating the various parts of the date string as extracted by the second FOR command.

call :getfiledatestr path\file1.txt file1time
call :getfiledatestr path\file2.txt file2time
if %file1time% equ %file2time% (
  echo path\file1.txt is the same age as path\file2.txt to within a minute
) else if %file1time% lss %file2time% (
  echo path\file1.txt is older than path\file2.txt
) else (
  echo path\file1.txt is newer than path\file2.txt
)
goto :eof

@REM usage:
@REM :getfiledatestr file-path envvar
@REM result returned in %envvar%
:getfiledatestr
for %%f in (%1) do set getfiledatestr=%%~tf
@REM for MM/DD/YYYY HH:MM AMPM use call :appendpadded %2 %%c %%b %%a %%f %%d %%e
@REM for DD/MM/YYYY HH:MM AMPM use call :appendpadded %2 %%c %%b %%a %%f %%d %%e
@REM for YYYY/DD/MM HH:MM AMPM use call :appendpadded %2 %%a %%b %%c %%f %%d %%e
set %2=
for /f "tokens=1,2,3,4,5,6 delims=/: " %%a in ("%getfiledatestr%") do (
    call :appendpadded %2 %%c %%b %%a %%f %%d %%e
)
@goto :eof

@REM Takes an env var as the first parameter
@REM and values to be appended as the remaining parameters,
@REM right-padding all values with leading 0's to 4 places
:appendpadded
set temp_value=000%2
call :expand set %1=%%%1%%%%temp_value:~-4%%
shift /2
if "%2" neq "" goto appendpadded
set temp_value=
@goto :eof

@REM forces all variables to expand fully
:expand
%*
@goto :eof

回答5:

For one specific situation wherein you want to do something in the style of a Makefile, overwriting a destination file based on a source file only if the source file is newer, I came up with this hideous but simple method. This is only an option if you don't care in any way about the existing contents of a destination file that's older than the source file.

for /f "delims=" %%r in ('xcopy /D /Y /f /e "%inputdir%\%source_filename%" "%outputdir%\%dest_filename%"') do (
  IF "%%r" EQU "1 File(s) copied" %build_command% "%inputdir%\%source_filename%" "%outputdir%\%dest_filename%"
)

What this does is, xcopy only overwrites the destination file if the origin file is newer. If it's not newer, %%r is "0 File(s) copied", so the conditional command doesn't execute, and the destination file is never overwritten. If it is newer, %%r is "1 File(s) copied", so your destination file is briefly a copy of the source file, then the build command gets executed, replacing it with a new version of whatever the destination file is actually supposed to be.

I should probably have just written a perl script.

(Note: you can also have xcopy handle the situation where the destination file doesn't initially exist, by putting an asterisk at the end of the destination filename; if you don't do that then xcopy isn't sure whether the destination is a filename or folder name and there is no flag to default the answer to filename.)

回答6:

Based on Wes answer I created updated script. The updates got too numerous to put into comments.

1. I added support for one more date format: a format including dots in dates. Added instructions about how to enable more date formats.
2. The Wes answer actually did not work since cmd is not able to compare integers larger than 1+31 bits, so I fixed that with converting the numeric strings to quoted numeric strings.
3. The script is able to consider missing files as oldest files.
4. Added support for second precision.

My version is below.

@REM usage:
@REM :getfiledatestr file-path envvar
@REM result returned in %envvar%
:getfiledatestr


for %%A in (%1) do (
    set getfilefolderstr=%%~dpA
    set getfilenamestr=%%~nxA
)

@REM Removing trailing backslash
if %getfilefolderstr:~-1%==\ set getfilefolderstr=%getfilefolderstr:~0,-1%

@REM clear it for case that the forfiles command fails
set getfiledatestr=

for /f "delims=" %%i in ('"forfiles /p ""%getfilefolderstr%"" /m ""%getfilenamestr%"" /c "cmd /c echo @fdate @ftime" "') do set getfiledatestr=%%i
@REM old code: for %%f in (%1) do set getfiledatestr=%%~tf

set %2=

@REM consider missing files as oldest files
if "%getfiledatestr%" equ "" set %2=""

@REM Currently supported date part delimiters are /:. and space. You may need to add more delimiters to the following line if your date format contains alternative delimiters too. If you do not do that then the parsed dates will be entirely arbitrarily structured and comparisons misbehave.
for /f "tokens=1,2,3,4,5,6 delims=/:. " %%a in ("%getfiledatestr%") do (

@REM for MM/DD/YYYY HH:MM:SS AMPM use call :appendpadded %2 %%c %%b %%a %%g %%d %%e %%f
@REM for DD/MM/YYYY HH:MM:SS AMPM use call :appendpadded %2 %%c %%b %%a %%g %%d %%e %%f
@REM for YYYY/DD/MM HH:MM:SS AMPM use call :appendpadded %2 %%a %%b %%c %%g %%d %%e %%f
    call :appendpadded %2 %%c %%b %%a %%g %%d %%e %%f
)

@goto :eof


@REM Takes an env var as the first parameter
@REM and values to be appended as the remaining parameters,
@REM right-padding all values with leading 0's to 4 places
:appendpadded
set temp_value=000%2
call :expand set %1=%%%1%%%%temp_value:~-4%%
shift /2
if "%2" neq "" goto appendpadded
set temp_value=

@REM cmd is not able to compare integers larger than 1+31 bits, so lets convert them to quoted numeric strings instead. The current implementation generates numeric strings much longer than 31 bit integers worth.
call :expand set %1="%%%1%%%"

@goto :eof


@REM forces all variables to expand fully
:expand
%*
@goto :eof