I generally tell people that, once a script is longer than ~100 lines and/or you start adding functions, you're probably better off with something like Python.
I know that's not a popular opinion with shell enthusiasts, but it's saved me so much frustration both in writing new scripts and coming back to them later for refactoring.
In the past I almost exclusively used Python, but I'm starting to like Go.
The practice of programming in shell languages was well established when Bash was designed and Bash was definitely designed with that use in mind. So by your definition Bash is a "real" programming language.
Lisp on the other hand, was much more designed as a system and formal notation to reason about certain classes of logic problems.. So, Lisp is not a "real" language?
No, it can not.
You can definitely tell there's a different "feel" to bash and Tcl, Python, Perl, Go, etc, yes? Shell languages basically evolved out of batch processing languages that were meant to only run programs in sequence and it shows.
Agreed. My threshold is usually "when you want to start using arrays or dictionaries". I find bash best for file manipulation and running programs in other languages
I never even bothered to learn Bash properly because even that's difficult, and I figured it'd be "good mental money after bad". And, now that Python ships with all distros, I feel even less need to.
I do like Bash's range syntax though:
for i in {0..5} ; do echo $i ; done
echo {1..5}
echo {1..5}{1..5}{1..5}I am curious if people will uptake PowerShell Core (though not much of a fan there either).
If you need >100 lines of code your code is too complex in the script world, and you should split it into several scripts where each does one thing, and that one thing well. Usually, bash scripts are applied with pipes. A sequence like cat x | tr a b | sort >output is much more likely and easy to handle then a single script which does all these things.
KISS with Bash is a very different approach compared to other scripting languages like Python and Perl. There you can write long code easily and conveniently. However, things can get tough when larger scripts need to be maintained.
I consider the examples in the "Bash Bible" a collection of useful black boxes. It's fine if they just work. Regarding the "unreadable" trim_string for instance, if you have problems to understand that code, and you have to change something then you can simply write your own new trim_string script, even in Python or Perl if you like. Pipes work also well with them.
Update: Another advantage of bash and pipes over Python/Perl is that the Unix system can assign each script in a pipe to a separate thread. That means, simple bash scripts with pipes can work _much_ faster than single scripts in Python or Perl.