Exiting from scripts and exit codes

We are now well familiar with shell script files, commands, and running them in bash to get the desired output. Until now, whatever shell script examples we have seen, they run line by line until the end of the file. While writing real-world shell scripts, it may not always be the case. We may need to exit a script in between, for example, when some error occurs, doesn't satisfy a certain condition, and so on. To exit from the script, the exit shell builtin is used with an optional return value. The return value tells the exit code, which is also known as return status or exit status.

Exit codes

Every command returns an exit code when it gets executed. Exit code is one of the ways to know whether a command is executed successfully or if some error has occurred. As per the POSIX (Portable Operating System Interface) standard convention, a command or program with successful execution returns 0, and 1 or a higher value for failed execution.

In bash, to see...