Introduction of posix output [WIP]

[matejak]

This PR aims to implement the posix script output as introduced in #31.
The work can be logically divided into two cathegories:

• Common effort towards reducing usage of arrays both for posix and bash outputs.
• Specialized effort to introduce specialized versions of macros specific to the POSIX output.

[the-real-neil]

I have yet to test this patch, but it looks completely different than what I was expecting --- in a good way. You may have inspired me to get back into m4 hacking.

[the-real-neil]

It's not working for me:

$ ./bin/argbash -t posix-script - <resources/examples/minimal.m4 >minimal.sh && sh minimal.sh
minimal.sh: 37: minimal.sh: Syntax error: "(" unexpected

[matejak]

Thank you for following, this work is still a WIP and it will take some time.
I have to say that I am not comfortable writing and reading from the disc just to get arguments parsed, so I will think further of how to do that. There is the positional args array and the local keyword that have to be dealt with and unless those are addressed, it won't work.
Some of the work could be nicely resolved by going for the strict POSIX compliance (i.e. scripts aren't allowed to use long options and there can't be optional args after the first positional argument). Then, Argbash could generate a parsing loop that would use getopts, which would be pretty neat. Let's see...
m4 is a fascinating language and its extension m4sugar is even quite nice to use, so I am happy to hear that :-)

[the-real-neil]

Regarding the use of temporary files to implement argument parsing: it's a trick I use often in my own scripting but it's a poor fit for argbash if your intent is to avoid dependencies on any file system.

Regarding your point about getopts: while its presence is guaranteed by POSIX, I think sacrificing long options is a mistake. You've already done the considerable work in implementing your own argument parsing mechanism. If it can be adapted to avoid Bashisms, then all kinds of shells stand to benefit, not just the strictly POSIX-compliant ones.

[the-real-neil]

@matejak , this is probably the least of your concerns, but the local keyword is not POSIX. dash tolerates it, though.

[matejak]

That's fine, I am very close to getting rid of local for POSIX output.

[matejak]

The POSIX output is now generally usable and just needs some polishing.