Substitution

Question 1

Back quotes

Answer 1

>MYDIR=dirname /usr/local/share/doc/foo/foo.txt

>echo $MYDIR /usr/local/share/doc/foo

• substitution by the result of the command inside the back quotes

Question 2

$( )

Answer 2

>MYDIR=$(dirname /usr/local/share/doc/foo/foo.txt)

>echo $MYDIR /usr/local/share/doc/foo

• Substitution by the result of the command inside the parenthesis behind the $ sign

Question 3

Substitute the result of piped commands

Answer 3

>MYFILES=$(ls /etc | grep pa)

>echo $MYFILES

pam. d passwd
* Note we’re listing the contents of the /etc directory whose name starts with the string “pa”