Wlid Cards in Linux

Wild Cards :- 

A character or string used for pattern matching

Expand the wild card pattern into a list of file and/or directories.(path)

wild cards can be used with most commands ex:- ls, rm, cp etc

Some basic wild cards are:  

• *  -  matches zero or more characters
•  ?  -  matches exactly one characters
•  [ ]   -  matches any of the characters included between the brackets matches a single character 

* as Wild Card:* matches zero or more characters:-

• *.txt -  Files those ends with .txt 
• a*  -  Files those start with a
• a*.txt -  Files those start with a and end with .txt

ls *.txt
ls a*
ls a*.txt

  ? as Wild Card:

?  matches exactly one character:- 

• ?  -   Files those have one character
•  ?.txt -  Files those have one character and ends with .txt 
•  a?.txt  -  Files those start with a and have one more character and end with .txt

ls ?
ls ?.txt
ls ??.txt
ls a?.txt

[] as Wild Card:

    [] matches any of the characters included between the brackets match a single character

• ca[nt]*  -  Files start with ca and have n or t in it and have more character after n or t like – cat, can, candy, catch etc.  
•  [!]  -  Exclude any character  ex:-   [!abc]  -  Files start with a, b, c will be excluded

la ca[nt]*
ls *.txt
ls [!ae]*.txt

Wild Card – Range:

   Use two character separated by a hyphen to create a range in character class

• [a-e]  -  Matches all files start with a, b, c, d or  
•  [1-4]  -  Matches all files start with 1, 2, 3 or 4

ls *.txt

ls [a-e]*.txt

Matching Wild Card Patterns:

\   -  Escape character. Use if you want to match a wild card character

• *\?  -   Matches all files that ends with a question mark 

ls *\?

Nmae Character Classes:   

•   [[:alpha:]]  -  All alphabatical letters lower and upper case
•  [[:upper:]]  -  Upper case alphabatics 
•  [[:lower:]]  -  Lower case alphabatics 
•  [[:alnum:]]  -  Alphabatical letters (lower and upper case) and Digit 
•  [[::digit:]]  -  Only digit
• [[:space:]]  -  Such as spaces, tab, new line characters

ls *[[:upper:]].txt

ls *[[:digit:]].txt

ls *[[:digit:]]*