`$?` is a variable that holds the return value of the last executed command.
`echo $?` displays 0 if the last command has been successfully executed and displays a non-zero value if some error has occurred.
The bash sets `$?` To the exit status of the last executed process. By convention 0 is a successful exit and non-zero indicates some kind of error. It can be used to check if the previous command has been executed without any errors. If it has executed successfully then it stores 0. `$?` is also useful in shell scripts as a way to decide what to do depending on how the last executed command worked by checking the exit status.
```console
$ random-binary ; echo $?
<...>
<theexitstatusofrandom-binary>
$
```
> You have to use Man or Google to know more about commands flags, in order to solve this exercise!