China DOS Union

Under 98 or 2000, for example if the current system date is 20051218, then how can I get the previous day's date 20051217 in a batch file?

This problem of yours is super complicated. You need to consider whether the current date is the 1st; if it is, then you also have to consider how many days were in the previous month, and whether it's a leap year or a common year. Here's an example for getting the date under 2000, try improving it yourself!

1. ::Get the date
   
2. rem Please improve it yourself
   
3. @echo off
   
4. for /f "tokens=1,2,3 delims=-/. " %%a in ('date /t') do (
   
5. set A=%%a
   
6. set B=%%b
   
7. set C=%%c
   
8. )
   
9. rem set /a C-=1
   
10. echo %A%%B%%C%
    

-=Code coloring BY：无奈何=-

Use GNU date:

.\date -d "-1 day" "+%Y%m%d"

Re xolbm:

This question has different answers on different platforms.

Under 2000's cmd, you can convert the date into a relative value from some earlier date, then do arithmetic on that value, and then convert it back into the new date.

Under 98's command, you can use a marker method: each day when the program runs, mark today's date, and take yesterday's date from the previous mark. But this algorithm requires the program to be run at least once every day.

A more general method is to use a third-party command-line program, such as date, but then it loses the characteristics of a batch script program.

Since this topic has been discussed many times before, the code and programs for the above solutions can all be found in older posts, such as the link below, so please make good use of the search function:

(Solved) How to delete files older than N days from the DOS command line under WINDOWS
http://www.cn-dos.net/forum/viewthread.php?tid=16676

Originally posted by tigerpower at 2005-12-19 22:38:
Use GNU date:

.\date -d "-1 day" "+%Y%m%d"

Haha, using a different tool makes it much simpler. Those little tools under UNIX really are powerful.

Thank you, teachers, for your guidance! It looks like using a batch program to add or subtract system time is quite difficult for a newbie like me!
Thanks again, teachers, for your guidance!!

Yeah. The batch commands above already made me dizzy. Better to just write a small program directly, much more convenient. HOHO

Great, I'll try it first