in reply to can't open file for appending
Does the D:/log_script/tuxedo_logs directory still exist?
Does the script run as you or another user? If it runs as a different user, does that user have permission to write to the D:/log_script/tuxedo_logs directory?
As I was writing this up I noticed that the filename in the error you posted doesn't match the filename that the code as shown would generate... The error has it as 'D:/log_script/tuxedo_logs/startup.20170814xxxxxx.log' but the script as written would generate them like 'D:/log_script/tuxedo_logs/startup20170814xxxxxx.log' (notice the lack of a period after startup). I assume you typed the error message (and included a period that wasn't there) instead of copy/pasting it.