[gdavisson]

bash is the default interactive shell for users, but dash is the default shell for scripts with a #!/bin/sh shebang (or no shebang, unless they're run from bash), system() calls, etc. This means bashisms will work sometimes, which can be worse than not working at all.

I agree about the importance of differentiating bashisms from basic scripting, but I think the root cause of that is documentation (including this book) that don't make the distinction.

[layer8]

The book is very clear about the fact that it’s using Bash, even noting when a feature requires a newer version, and uses #!/bin/bash for scripts throughout.

[John23832]

...But the foreword for any script could just as easily be `#!/bin/bash`... you're choosing not to use bash. If you're on a system with no bash, and are forced to use `sh`, then just don't use bashisms...

I'm not trying to be difficult, but I just don't see a problem. Explicitly use bash (or a derivative) if you want bashisms, don't if you do not.