There are single quotation marks, double quotation marks, and back quotation marks in the shell, each of which is used differently. Here is a summary of the use of quotation marks in the shell

Single quotes

str='this is a string'

Single-quotation string features:

  • Any character in a single quote is printed as it is. Variables in a single quote string are invalid.
  • A single quote cannot appear in a single quote string (even if you use an escape character for a single quote).

Double quotation marks

myname='Yuan'
str="My name is  \"$myname\"! \n"

Features of double quotation marks:

  • You can have variables in double quotes
  • Escape characters can appear in double quotation marks

The quotation marks

line = `sed -n '/string/=' test.txt | sed -n "1"p`
echo $line

The purpose of the backquotes is to store the result of many commands in a variable