The difference between $() and $of linux

What is the difference between $and $? This problem may be encountered in our daily work. Through this question, I hope you can harvest more. If you don't look at the answer, don't know if you can answer this question with confidence? Let's try it.

Linux $() $Difference

$

The symbol for $is in different places, and the definition it represents will vary. For example, in bash, the $symbol indicates that the current user is a normal user; in bash scripts.$ Start with a variable.

For example, here are some special variables:

$indicates the number of parameters

$0 is the name of the script itself

$1 is the first parameter passed to the shell script

$2 is the second argument passed to the shell script

$@ means all parameters, and all parameters are independent

$is the current process ID number of the running script

That $is the exit status showing the final command, 0 means no errors, and the other means errors.

$()

$(): This parenthesis contains the command, which acts the same as `` backquotes. Execute this command

For example, the function of $(command) is to execute the command and output the result (of course, this output is not on the screen, but in the specific context).

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