How Linux looks for a specific character file or directory

1. Display all files or directories with L, ending with a lowercase letter, and with at least one digit in the middle of the/var directory

2. display files or directories that start with any digit in the/etc directory and end with a non-digit

3, display/etc/directory with a non-letter beginning, followed by a letter and any other arbitrary length of any character file or directory

4. Display all the numbers in the/etc/directory starting with RC, followed by 0-6, other files or directories of any character

5. Display all files or directories ending with. D in the/etc directory

How Linux looks for a specific character file or directory