Re: How to enter escape character in a positional string argumentfrom the command line?

[Barry]

> On 21 Dec 2022, at 17:06, Chris Angelico  wrote:
> 
> On Thu, 22 Dec 2022 at 03:58, gene heskett  wrote:
>> 
>>> On 12/21/22 11:22, Chris Angelico wrote:
>>> On Thu, 22 Dec 2022 at 03:11, Stefan Ram  wrote:
 
 Lars Liedtke  writes:
> Or you could have "native" bash ($SHELL) with WSL.
 
   In this newsgroup, it would actually be obvious to use Python.
>>> 
>>> Less obvious than you might think - partly because bash is just so
>>> dang good that it's really really hard to outdo it :) Sure, bash has a
>>> lot of weird and wonky edge cases, but it's an incredibly practical
>>> shell to use.
>>> 
>> When you make a statement like that, Chris, you should also note that
>> every single one of those "wonky edge cases" is documented down to the
>> last dotted i. Bash's docs will kill a good sized pulp tree, needing
>> around a ream of paper to print on a duplex printer. I know, I did it
>> around a decade ago. If you like to write scripts, having a dead tree
>> copy of the docs at your elbow in incredibly useful.  That huge man page
>> does not cover it like the printed docs do.
>> 
> 
> Oh yes, absolutely true. Its wonkiness is dependable and consistent;
> but it is definitely quirky (look at all the different ways to embed
> arguments into things, and the ways that $*, $@, "$*, and "$@" behave
> when put into variables). Not usually a problem, but it does sometimes
> leave you thinking "wow, wouldn't it be easier to just use something
> like Python?". And in the complicated cases, yeah, it can be. But in
> the simple cases? Bash rocks.

I see bash scripts that are 1000’s of line of code at work and its a 
maintenance nightmare.

Knowing when to make the move from “handy bash script” to “this is a production 
application” and needs to be python is what I see people miss.

After a certain point in complexity the python code wins on maintenance.
Personally i set a low bar to move from bash to python.

Barry


> 
> ChrisA
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> 

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Re: How to enter escape character in a positional string argumentfrom the command line?

[Chris Angelico]

On Thu, 22 Dec 2022 at 04:12, Barry  wrote:
> I see bash scripts that are 1000’s of line of code at work and its a 
> maintenance nightmare.
>
> Knowing when to make the move from “handy bash script” to “this is a 
> production application” and needs to be python is what I see people miss.
>
> After a certain point in complexity the python code wins on maintenance.
> Personally i set a low bar to move from bash to python.

Agreed 100%. However, how many commands do you type a day at the bash
prompt? *Every one of those* is a simple case that doesn't need
Python. That's what makes bash such a great shell. You can type
simple, convenient commands, and they *just work*. Need something a
bit more complicated? You can do that too. Want to automate a short
sequence of commands? Don't have to translate them into another system
(like Python subprocess calls), just copy/paste them into a shell
script.

Yes, there absolutely is a point beyond which it's better to translate
everything. But the vast number of commands executed every day? Most
of them are fine with bash. And that's why Python will never replace
bash as a shell.

ChrisA
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Re: How to enter escape character in a positional string argumentfrom the command line?

[Chris Angelico]

On Thu, 22 Dec 2022 at 03:58, gene heskett  wrote:
>
> On 12/21/22 11:22, Chris Angelico wrote:
> > On Thu, 22 Dec 2022 at 03:11, Stefan Ram  wrote:
> >>
> >> Lars Liedtke  writes:
> >>> Or you could have "native" bash ($SHELL) with WSL.
> >>
> >>In this newsgroup, it would actually be obvious to use Python.
> >
> > Less obvious than you might think - partly because bash is just so
> > dang good that it's really really hard to outdo it :) Sure, bash has a
> > lot of weird and wonky edge cases, but it's an incredibly practical
> > shell to use.
> >
> When you make a statement like that, Chris, you should also note that
> every single one of those "wonky edge cases" is documented down to the
> last dotted i. Bash's docs will kill a good sized pulp tree, needing
> around a ream of paper to print on a duplex printer. I know, I did it
> around a decade ago. If you like to write scripts, having a dead tree
> copy of the docs at your elbow in incredibly useful.  That huge man page
> does not cover it like the printed docs do.
>

Oh yes, absolutely true. Its wonkiness is dependable and consistent;
but it is definitely quirky (look at all the different ways to embed
arguments into things, and the ways that $*, $@, "$*, and "$@" behave
when put into variables). Not usually a problem, but it does sometimes
leave you thinking "wow, wouldn't it be easier to just use something
like Python?". And in the complicated cases, yeah, it can be. But in
the simple cases? Bash rocks.

ChrisA
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Re: How to enter escape character in a positional string argumentfrom the command line?

[gene heskett]

On 12/21/22 11:22, Chris Angelico wrote:

On Thu, 22 Dec 2022 at 03:11, Stefan Ram  wrote:


Lars Liedtke  writes:

Or you could have "native" bash ($SHELL) with WSL.


   In this newsgroup, it would actually be obvious to use Python.


Less obvious than you might think - partly because bash is just so
dang good that it's really really hard to outdo it :) Sure, bash has a
lot of weird and wonky edge cases, but it's an incredibly practical
shell to use.

When you make a statement like that, Chris, you should also note that 
every single one of those "wonky edge cases" is documented down to the 
last dotted i. Bash's docs will kill a good sized pulp tree, needing 
around a ream of paper to print on a duplex printer. I know, I did it 
around a decade ago. If you like to write scripts, having a dead tree 
copy of the docs at your elbow in incredibly useful.  That huge man page 
does not cover it like the printed docs do.



   When commands are typed manually, this might be a bit verbose,
   though. I mean

os.chdir( r'C:\EXAMPLE' )

   versus

CD C:\EXAMPLE


Exactly. What's good for a programming language is often not good for a shell.


class PythonShell( cmd.Cmd ):

 intro = 'Welcome to the Python shell. Type help or ? to list commands.\n'
 prompt = '(Python) '
 file = None

 def do_cd( self, arg ):
 'change directory:  CD C:\EXAMPLE'
 os.chdir( *parse( arg ))

 def do_bye( self, arg ):
 'Exit:  BYE'
 print( 'Thank you for using the Python Shell!' )
 return True


Sure, you can always create your own shell. But I think you'll find
that, as you start expanding on this, you'll end up leaning more
towards "implementing bash-like and/or cmd-like semantics in Python"
rather than "creating a Python shell". Shells, in general, try to
execute programs as easily and conveniently as possible. Programming
languages try to stay inside themselves and do things, with subprocess
spawning being a much less important task.

Fun challenge: see how much you can do in bash without ever forking to
another program. And by "fun", I mean extremely difficult, and by
"challenge" I really mean "something you might have to do when your
system is utterly hosed and all you have available is one root shell".

It's amazing how far you can go when your hard drive has crashed and
you desperately need to get one crucial login key that you thought you
had saved elsewhere but hadn't.

ChrisA


Cheers, Gene Heskett.
--
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 

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