The difference between a Linux shell, a double-quote "", a single quote ", and an anti-quote"

Learn a bash script today and see that there is a: bin= ' dirname '

(dirname filename is the directory where the file is exported, and $ is the file name of the bash file, which is generally used in bash to enter the directory where the script is located)

I tried the cat $bin

The output is:.

Then I'm going to take the anti-quote "' Out: Bin=dirname"

Error after running cat $bin.

I looked online for some of Bash's single-quote ', double-quote ' and ' anti-quote ' differences.

Single quote ' and double quote ' "

Both are the problem of resolving a space in the middle of a variable.

In bash, "whitespace" is a very special character, such as the str=this is String defined in bash, which will cause an error, using single quotes "and double quotes" in order to avoid errors.

The single quote ', double quote ' "is the difference between a single quote ' ' that deprives all characters of a special meaning, and a single quote ' inside a simple character. The double quotation mark "" is an exception to the argument substitution ($) and command substitution (") in the double quotation mark" ".

Say n=3.

Echo ' $n '

The result is N3.

Change it to double quotes, echo "$n," and the result is 3.

Anti-Quote "'

Anti-quote ' is command substitution, command substitution means that the shell can execute the command in the ', and the output will be saved temporarily, and output in the appropriate place. Syntax: ' Command '

In the following example, the command execution results are saved in a variable:

#!/bin/bash

DATE=`date`
echo "Date is $DATE"

USERS=`who | wc -l`
echo "Logged in user are $USERS"

UP=`date ; uptime`
echo "Uptime is $UP"

Operation Result:

Date is Thu Jul  2 03:59:57 MST 2009
Logged in user are 1
Uptime is Thu Jul  2 03:59:57 MST 2009
03:59:57 up 20 days, 14:03,  1 user,  load avg: 0.13, 0.07, 0.15

  

	
   


  

The difference between a Linux shell, a double-quote "", a single quote ", and an anti-quote"