Pattern Matching

 

Command	Options	Description
*		Matches any number of character including NONE. * does not match all files beginning with dot <.>.
	ls -l chap*	Matches all the files which starts with chap.
	ls -x chap*	Matches all the files which starts with chap and prints in multi column way.
?		Matches single character.
	ls -l chap?	Matches all the files with only 5 character name and should start with chap.
[ ijk ]		Matches single character either i or j or k.
[ !ijk ]		Matches single character that is not i or j or k
[ x - z ]		Matches single character that is not within the ASCII range of character x and z.
[ ! x - z ]		Matches single character that is not within the ASCII range of character x and z
	ls -l chap0[1 - 4]	Range specification is also available.
	ls -l [ a – z A-Z]	Matches all file names beginning with alphabet irrespective of case.
	ls -l chap[!0 - 9]	Matches all file names beginning with alphabet chap and not ending with any number.
	ls *.ist	Print all the files which end with ist extensions.
	cp chap?? abc	Copy all files starts with chap to abc directory.
	cmp chap[12]	Compares file chap1 and chap2.
	mv *  ../bin	Moves all the files to bin directory.
	cat chap[!0 - 9]	Concatenates all the files beginning with chap and not ending with number.
	ls -l *	* does not match all files beginning with dot <.>.
	ls -l .???*	The above problem can be solved with specifying first few character using meta character <?> explicitly.
Escaping Backslash ( \ )		Playing with file names which uses meta character in their file name.
	ls - l chap*	Print all files whose names start with chap but not the one whose name is chap*.
	ls - l chap\*	The above problem can be solved by escaping the special character.
Pipe |		To pass the standard output of one command as the standard input to another.
	who | wc -l	Output of who command <three users> passed as input to wc which count the number of lines present.
Tee	who | tee users list	Tee saves the output of who command in user list as well as display it also.
Shell Variable		Shell variables are initialized to null value < by default > so it returns null. All words starts with $ are considered as variable unless single quoted or escaped.
	a=ab, b=cd, z=$a$b. echo $z	shell concatenate two variable.
	echo '$10' eg: $10	All words starts with $ are considered as variable unless single quoted or escaped.
	echo "$10" eg: 0	Shell is looking for $1 variable which is undefined so passes null for this. $1 is part of positional parameter.