formatted date in Windows script

I find the output of the full date command in Windows lacking. Thus, I was trying to find a way to date/time stamp a logfile in a Windows batch script.
C:\WINNT>date /t
Tue 10/28/2008

I only wanted YYYYMMDD_HHmm, where
YYYY = four digit year
MM = two digit day
DD = two digit month
HH = two digit hour
mm = two digit minute

So, I needed to combine outputs from both the Windows date and time functions.

My batch script ended up looking like this:
set dt=%date:~-4%%date:~4,2%%date:~7,2%_%time:~0,2%%time:~3,2%
bash "siteBackupAll.sh" | tee log%dt%.txt

In the example above, the resulting script outputs a logfile named:
log20081028_1433.txt

The Windows help for SET is pretty cryptic, much like any Unix man page. You can see all the options for Windows shell programming (variables, operators, expressions, etc) if you type
SET /?

at the command prompt.

Variable expansion in Windows is a little weird. Here is a snip from the help, but essentially, you can act on the expansion of a variable (ie, pluck parts from the output) by using a numbering scheme that will start counting from the left or right, depending on whether the number you specify is positive (start from left) or negative (start from right). In essence, the numbering is much like any programmatic substr (substring) function:

May also specify substrings for an expansion. %PATH:~10,5%would expand the PATH environment variable, and then use only the 5characters that begin at the 11th (offset 10) character of the expandedresult. If the length is not specified, then it defaults to theremainder of the variable value. If either number (offset or length) isnegative, then the number used is the length of the environment variablevalue added to the offset or length specified.

%PATH:~-10%would extract the last 10 characters of the PATH variable.
%PATH:~0,-2%would extract all but the last 2 characters of the PATH variable.

'sodo

command line date time change

Or how to set the time in Linux.

Here's another thing I always forget: how to change the date or time at the command line, preferably using the Bourne shell in Linux.

Example:
To change the date/time on a Linux box to September 10, 2008 at 5:37pm, enter the following:
date 0910173708

The ordering of the fields is a bit odd, so pay attention.

where the date/time format is the following:
MMDDHHmmYY
MM - two digit month
DD - two digit day
HH - two digit hour
mm - two digit minute
YY - two digit year

All are zero padded if date/time values are below 10.

Changing the date time was never easier!

enjoy,
sodo