3You type in echo into the terminal and it prints out 0 Did

(3)You type in “echo $?” into the terminal and it prints out 0. Did the command you entered immediately before “echo $?” execute successfully?

Solution

Please follow the data and description :

Exit Status :

Each and every Linux command in general returns a status when it terminates normally or abnormally. The user can use this in the shell script to display an error message or to take some sort of action. As an example, if the \'tar\' command is unsuccessful, it returns a code which tells the shell script to send an e-mail to sys admin and so on for the preceeding response.

The exit status is an integer variable number that is returned. In the resposne if the value is a 0 as the exit status then that means the command was successful without any errors. And any non-zero that is between 1-255 as the exit status conveys that the imeediate preceeding command was a failure. And to to get the exit status of the previously executed command there can be used a special shell variable represented as ? .

As an example let us see the below execution process and the respective results :

date
echo $?

this results the output as :
0

Now that we try with a non-existence command :

foobar123 # not a valid command
echo $? # print exit status

this results the output as :

2

The status exit status is 0 if OK, 1 if minor problems, 2 if serious trouble.

Hope this is helpful.