Get random numbers under BASH and DOS
Both Linux Bash and Windows DOS support random number generation. The random number is ‘stored’ in a system environment variable named “RANDOM” (I believe this variable links to a script to generate the actual random numbers on both systems), use it in the same way as you use other ENV variables. E.g.
On Linux:
1 | echo $RANDOM |
;
On Windows：
1 |
;
Share this:
What about use %RANDOM% inside FOR in ms-DOS
ex:
FOR /L %%a IN (0,1,100) DO @echo %RANDOM%
I would generate 100 DIFFERENT random numbers but the line above generates 100 times the same number!!! What’s up?
Aha! random, you are in trouble with the so-called “delayed variable expansion” in DOS batch. This has been discussed here: http://blogs.msdn.com/b/oldnewthing/archive/2006/08/23/714650.aspx .
In your case, in order to get 100 DIFFERENT random numbers, you have to enable the delayed variable expansion for your DOS console. Do this “cmd /v” to start it, or add this “setlocal enabledelayexpansion” in your batch file. Then, another important thing is to change the “%” symbol to “!” for the variables you want them to be expanded on the fly. E.g. try
“FOR /L %%a IN (0,1,100) DO @echo !RANDOM!” in your file, you’ll get 100 DIFFERENT random numbers!