China DOS Union

Format: if exist file name　 command to be executed
If the specified file exists, the condition is true, and the command is run; otherwise, the next sentence is run

If there are two or more commands to be executed, how should they be written?

Another question:
Find a segment of statements to have the following effect.
If 01.txt and 02.txt exist simultaneously under D:\
Then open the contents of 01.txt and 02.txt
Otherwise, delete 01.txt (or 02.txt) when only 01.txt or 02.txt exists

Looking forward to an answer~~~

1. if exist 1.txt if exist 2.txt (start "" 1.txt && start "" 2.txt)
2.
@echo off dir /a-d 1.txt || goto next dir /a-d 2.txt || goto next start "" 1.txt & start "" 2.txt goto :eof :next del 1.txt 2.txt 2>nul goto :eof
The code has not been tested...

Thanks. . .
Let's try first.

Merge the code for 2F, which should meet the LZ's requirement:
@echo off if exist 1.txt if exist 2.txt (start "" 1.txt && start "" 2.txt) else (del 1.txt 2.txt 2>nul)

What is the usage of || here? Is it a logical operation?
And what does the '''' in front of 1.txt mean?

1、 & command1 & command2 Used to separate multiple commands in a command line. Cmd.exe runs the first command and then the second command. && command1 && command2 Used to run the command after the && only if the command before the && is successful. Cmd.exe runs the first command and then runs the second command only if the first command runs successfully. || command1 || command2 Used to run the command after the || only if the command before the || fails. Cmd.exe runs the first command and then runs the second command only if the first command fails to run successfully (receives an error code greater than zero). ( ) (command1 & command2) Used to group or nest multiple commands. ; or , command1 parameter1;parameter2 Used to separate command parameters. Note The "and" symbol (&), pipe symbol (|), and parentheses () are special characters. When passing them as parameters, you must prefix them with the escape character (^) or quotes. If a command successfully completes an operation, the command returns a zero (0) exit code or no exit code. For detailed information about exit codes, refer to the Microsoft Windows Resource Kit.
　　2、 START "title" The title displayed in the window title bar. 　　……
When the filename is a path with spaces, you must enclose the path in quotes. At this time, in order to prevent start from treating the path as the title, insert a pair of quotes between start and the path to distinguish the title from the path.

Um, learning. Thanks

if exist filename.txt ( echo 1 echo 2 echo 3 ) else ( echo 4 echo 5 echo 6 )

This format might be more convenient to use.