What are common special characters?

Common special characters in shell scripting include:

1. $ - Used for variable expansion.
2. * - Wildcard for matching multiple files or patterns.
3. ? - Wildcard for matching a single character.
4. & - Used to run processes in the background.
5. | - Pipe operator for passing output from one command to another.
6. ; - Command separator to execute multiple commands in sequence.
7. > - Redirects output to a file (overwrite).
8. >> - Redirects output to a file (append).
9. < - Redirects input from a file.
10. " and ' - Used for quoting strings; double quotes allow variable expansion, while single quotes do not.
11. \ - Escape character to treat the following character literally.

These characters have specific functions and meanings in the shell, so it's important to escape them when you want to use them as regular characters.