File Metacharacters

Shell metacharacters have special meaning and are used on the LINUX command-line to match file names.
The Shell expands them for you unless they are in single quotes or escaped! (more on escaping later)
Be careful, it can be confusing because the shell recognizes one set of symbols for file name substitution, while programs that process the contents of files (like sed and grep) use a different set, which are called regular expressions.

Shell Metacharacters for File-Name Substitution
*	matches zero or more characters of any type
?	matches exactly one character of any type
[]	matches any single character listed within the brackets. You can use a dash to specify a range of characters, for instance a-z.
[!c]	if the first character listed inside the brackets is '!', it matches any single character that is NOT in the brackets.

Here's an example:

 ls [Aa]??.*[0-9]

Matches any files starting with 'A' or 'a', followed by any two characters followed by '.' followed by anything else and ending with a numeric digit 0 thru 9. For example will match the following files:

 Ab2.9 alt.txt9 Aaa.123 a_..Z12b7

If you want the shell to use a character without its special meaning, you must escape it or put in in single quotes. For instance, try each of these and notice the difference:

echo *
echo '*'
echo \*

Before using metacharacters with a command like rm, it's a good idea to try them with ls first.