Wildcards

A wildcard is a character that can be used as a substitute for any class of characters. Wildcards are useful to perform actions on more than one file at a time.

Three types of wildcards are used with Linux commands. Those are

• Star Wildcard
• Question Mark Wildcard
• Square Brackets Wildcard

Star Wildcard ( * )

The character * matches zero or more characters in a file or directory name. Here are the examples.

$ ls a* : It displays all files starting letter ‘a’

$ ls b*t : It displays all files starting letter is ‘b’ and ending letter ‘t’

$ ls *g : It displays all files ending letter ‘g’

$ ls *.txt: It displays all text files (.txt)

$ ls *.html : It displays all html files (.html)

$ ls */* : It displays all files in all directories which are existed in current directory.

Question Mark Wildcard ( ? )

The character “?” can represent any single character. Below are the examples.

$ ls a?c : It displays all three character length files but starting letter is ‘a’ and ending letter is ‘c’.

$ ls b??k : It displays all four character files or directories but starting letter is ‘b’ and ending letter is ‘k’.

Square Brackets Wildcard []

It is used to specify range. It allows you to limit to a subset of characters. Below are the examples.

$ ls [aeiou]* : It displays all files but first character of the filename to listed must be any of the letters given with in the square bracket and remaining can be anything.

ls [!aeiou]* It displays all files whose first character is anything others than letters given in the square bracket.

$ ls [k-v]* : It displays all files whose starting letter is between k an v.

$ ls *[0-9]* : It displays all files whose name contains number from 0 to 9.