[moe]

Agreed. These toy-features are especially bitter when you look at how little bash the language has evolved in the past decade.

Pretty much every system out there drags a significant baggage of shell-scripts along. Yet there's been barely any improvement on the arcanest of all syntaxes. We keep on painstakingly reinventing ever the same control structures (half-broken lockfile mechanisms, retry loops, miserable support for pid/pgroups, awkward subprocess/fd handling etc. etc.) because for some reason nobody bothers to finally bake them into the shell.

It's become so bad that most teams seem to resort to using a different scripting language for complex tasks nowadays. But that comes with its own hairball of problems and imho the de-facto shell-scripting language simply should not fall behind its own problem domain so far that the preferred approach becomes to not use it.

[veyron]

Lets imagine for a moment that cross-platform backwards compatibility is a high priority, and that every change leads to a frustrated group of users running scripts from many years ago. How could you make a destructive change?

As an example, this works in bash 3.2 but not 4.0:

    diff <(awk '{print $1, $3}' file{1,2})

in 3 it expands to

    diff <(awk '{print $1, $3}' file1) <(awk '{print $1, $3}' file2)

whereas in 4 it expands to

    diff <(awk '{print $1, $3}' file1 file2)

[moe]

How could you make a destructive change?

Well, the same way that everyone else does it: by versioning.

The simplest approach would be to have /bin/bash2, /bin/bash3 etc., with /bin/bash defaulting to the last (current) unversioned bash release.

Then when you write a script that depends on a new feature you'd reference #!/bin/bash3 or whatever. More complex schemes are possible but probably not needed here. It's not rocket science.

And as your example illustrates: This kind of versioning is actually needed even in the current (almost stale) development-mode of bash. Its absence is the reason why many people still target sh as the lowest common denominator...

[veyron]

After some thought, what i'd like to see is what's done now with globstar (make new features accessible via shopt)