Learn Linux Shell Scripting - Fundamentals of Bash 4.4

Error checking

In the previous chapter, we spent some time explaining how we could capture and use user input in our scripts. While this makes our scripts much more dynamic and, by extension, much more practical, we also introduce a new concept: human error. Let's say you're writing a script where you want to present the user with a yes/no question. You might expect a reasonable user to use any of the following as an answer:

• y
• n
• Y
• N
• Yes
• No
• yes
• no
• YES
• NO

While Bash allows us to check for all values we can think of, sometimes a user will still be able to break the script by supplying input you do not expect. An example of this would be the user answering the yes/no question in their native language: ja, si, nei, or any of the countless other ...