I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?

--Jach

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Jach Feng wrote:

I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?

That depends on the command-line shell you're calling your script from.

In bash, you can include a newline in a quoted string:
./your_script 'step
'
(the closing quote is on the next line)

Or if you want to do it on a single line (or use other escape
sequences), you can use e.g.:
./your_script $'step\x0a'
(dollar sign before a single-quoted string which contains escape sequences)

--
Mark.

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Mark Bourne 在 2022年12月20日 星期二凌晨4:49:13 [UTC+8] 的信中寫道：

Jach Feng wrote:

I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?

That depends on the command-line shell you're calling your script from.

In bash, you can include a newline in a quoted string:
./your_script 'step
'
(the closing quote is on the next line)

Or if you want to do it on a single line (or use other escape
sequences), you can use e.g.:
./your_script $'step\x0a'
(dollar sign before a single-quoted string which contains escape sequences)

--
Mark.

That's really good for Linux user! How about Windows?

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On 12/19/2022 9:24 PM, Jach Feng wrote:

Mark Bourne 在 2022年12月20日 星期二凌晨4:49:13 [UTC+8] 的信中寫道：

Jach Feng wrote:

I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?

That depends on the command-line shell you're calling your script from.

In bash, you can include a newline in a quoted string:
./your_script 'step
'
(the closing quote is on the next line)

Or if you want to do it on a single line (or use other escape
sequences), you can use e.g.:
./your_script $'step\x0a'
(dollar sign before a single-quoted string which contains escape sequences) >>
--
Mark.

That's really good for Linux user! How about Windows?

One way is to process the argument after it gets into Python rather than before. How hard that will be depends on how general you need the
argument to be. For your actual example, the argument comes into Python
as if it were

arg1 = r"step\x0A" # or "step\\x0a"

You can see if there is an "\\x":

pos = arg1.find('\\x') # 4

Replace or use a regex to replace it:

arg1_fixed = arg1.replace('\\x0A', '\n')

Naturally, if "\\x0A" is only a special case and other combinations are possible, you will need to figure out what you need and do some more complicated processing.

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On 12/19/22, Jach Feng <jfong@ms4.hinet.net> wrote:

That's really good for Linux user! How about Windows?

In CMD, typing the "^" escape character at the end of a line ignores
the newline and prompts for "more" input. If you press enter again,
you'll get another "more" prompt in which you can write the rest of
the command line. Command-line arguments are separated by spaces, so
you have to start the next line with a space if you want it to be a
new argument. Also, "^" is a literal character when it's in a
double-quoted string, which requires careful use of quotes. For
example:

C:\>py -c "import sys; print(sys.orig_argv[3:])" spam^
More?
More? eggs^
More?
More? " and spam"
['spam\n', 'eggs\n and spam']

The above is easier in PowerShell, which supports entering multiline
strings without having to escape the newline. The second-level prompt
is ">> ". For example:

> py -c "import sys; print(sys.orig_argv[3:])" spam"
>> " eggs"
>> and spam"
['spam\n', 'eggs\n and spam']

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Thomas Passin 在 2022年12月20日 星期二上午11:36:41 [UTC+8] 的信中寫道：

On 12/19/2022 9:24 PM, Jach Feng wrote:

Mark Bourne 在 2022年12月20日 星期二凌晨4:49:13 [UTC+8] 的信中寫道：

Jach Feng wrote:

I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?

That depends on the command-line shell you're calling your script from. >>
In bash, you can include a newline in a quoted string:
./your_script 'step
'
(the closing quote is on the next line)

Or if you want to do it on a single line (or use other escape
sequences), you can use e.g.:
./your_script $'step\x0a'
(dollar sign before a single-quoted string which contains escape sequences)

--
Mark.

That's really good for Linux user! How about Windows?

One way is to process the argument after it gets into Python rather than before. How hard that will be depends on how general you need the
argument to be. For your actual example, the argument comes into Python
as if it were

arg1 = r"step\x0A" # or "step\\x0a"

You can see if there is an "\\x":

pos = arg1.find('\\x') # 4

Replace or use a regex to replace it:

arg1_fixed = arg1.replace('\\x0A', '\n')

Naturally, if "\\x0A" is only a special case and other combinations are possible, you will need to figure out what you need and do some more complicated processing.

That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)

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ery...@gmail.com 在 2022年12月20日 星期二中午12:35:52 [UTC+8] 的信中寫道：

On 12/19/22, Jach Feng <jf...@ms4.hinet.net> wrote:

That's really good for Linux user! How about Windows?

In CMD, typing the "^" escape character at the end of a line ignores
the newline and prompts for "more" input. If you press enter again,
you'll get another "more" prompt in which you can write the rest of
the command line. Command-line arguments are separated by spaces, so
you have to start the next line with a space if you want it to be a
new argument. Also, "^" is a literal character when it's in a
double-quoted string, which requires careful use of quotes. For
example:

py -c "import sys; print(sys.orig_argv[3:])" spam^

More?
More? eggs^
More?
More? " and spam"
['spam\n', 'eggs\n and spam']

The above is easier in PowerShell, which supports entering multiline
strings without having to escape the newline. The second-level prompt
is ">> ". For example:

py -c "import sys; print(sys.orig_argv[3:])" spam"

" eggs"
and spam"

['spam\n', 'eggs\n and spam']

Thanks for the information. No idea Windows CMD can take such a trick to enter "\n" :-)

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On Wed, 21 Dec 2022 at 15:28, Jach Feng <jfong@ms4.hinet.net> wrote:

That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)

Technically, Windows DOES have a shell similar to bash. It's called
bash. :) The trouble is, most people use cmd.exe instead.

ChrisA

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Chris Angelico 在 2022年12月21日 星期三下午1:02:01 [UTC+8] 的信中寫道：

On Wed, 21 Dec 2022 at 15:28, Jach Feng <jf...@ms4.hinet.net> wrote:

That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)

Technically, Windows DOES have a shell similar to bash. It's called
bash. :) The trouble is, most people use cmd.exe instead.

ChrisA

Really? Where? I can't find it in my Windows 8.1

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On Dec 21, 2022 06:01, Chris Angelico <rosuav@gmail.com> wrote:

On Wed, 21 Dec 2022 at 15:28, Jach Feng <jfong@ms4.hinet.net> wrote:
> That's what I am taking this path under Windows now, the ultimate
solution before Windows has shell similar to bash:-)

Technically, Windows DOES have a shell similar to bash. It's called
bash. :) The trouble is, most people use cmd.exe instead.

=====
I use Git Bash quite a lot: https://gitforwindows.org/
Is that the one you're referring to?

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Or you could have "native" bash ($SHELL) with WSL. But I assume not everyone is using it.

Cheers

Lars


Lars Liedtke
Software Entwickler

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Am 21.12.22 um 13:15 schrieb Albert-Jan Roskam:

On Dec 21, 2022 06:01, Chris Angelico <rosuav@gmail.com><mailto:rosuav@gmail.com> wrote:

On Wed, 21 Dec 2022 at 15:28, Jach Feng <jfong@ms4.hinet.net><mailto:jfong@ms4.hinet.net> wrote:
> That's what I am taking this path under Windows now, the ultimate
solution before Windows has shell similar to bash:-)

Technically, Windows DOES have a shell similar to bash. It's called
bash. :) The trouble is, most people use cmd.exe instead.

=====
I use Git Bash quite a lot: https://gitforwindows.org/
Is that the one you're referring to?

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Lars Liedtke <lal@solute.de> writes:

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

In this newsgroup, it would actually be obvious to use Python.
When commands are typed manually, this might be a bit verbose,
though. I mean

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

versus

CD C:\EXAMPLE

. But whenever one feels like writing a "batch file" for cmd,
"Power Shell" or bash, one could consider to use Python instead.

Then, of course, there "cmd", ...

import os
import cmd

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

def precmd(self, line):
line = line.lower()
return line

def parse( arg ):
return tuple( arg.split() )

print( __doc__ )
PythonShell().cmdloop()

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On Wed, 21 Dec 2022 at 23:16, Albert-Jan Roskam <sjeik_appie@hotmail.com> wrote:

On Dec 21, 2022 06:01, Chris Angelico <rosuav@gmail.com> wrote:

On Wed, 21 Dec 2022 at 15:28, Jach Feng <jfong@ms4.hinet.net> wrote:

That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)

Technically, Windows DOES have a shell similar to bash. It's called
bash. :) The trouble is, most people use cmd.exe instead.

=====

I use Git Bash quite a lot: https://gitforwindows.org/

Is that the one you're referring to?

Yeah, that's probably the easiest way to get hold of it.

ChrisA

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On Thu, 22 Dec 2022 at 03:11, Jach Feng <jfong@ms4.hinet.net> wrote:

Chris Angelico 在 2022年12月21日 星期三下午1:02:01 [UTC+8] 的信中寫道：

On Wed, 21 Dec 2022 at 15:28, Jach Feng <jf...@ms4.hinet.net> wrote:

That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)

Technically, Windows DOES have a shell similar to bash. It's called
bash. :) The trouble is, most people use cmd.exe instead.

ChrisA

Really? Where? I can't find it in my Windows 8.1

Ah, I didn't mean "ships with"; bash for Windows is very much
available, but you'd have to go fetch it. Try the Windows app store
first, and if not, a quick web search will find it. Or install Git for
Windows, which comes with bash.

ChrisA

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On Thu, 22 Dec 2022 at 03:11, Stefan Ram <ram@zedat.fu-berlin.de> wrote:

Lars Liedtke <lal@solute.de> 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 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

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On 21 Dec 2022 13:39:14 GMT, ram@zedat.fu-berlin.de (Stefan Ram) declaimed
the following:

Lars Liedtke <lal@solute.de> writes:

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

In this newsgroup, it would actually be obvious to use Python.
When commands are typed manually, this might be a bit verbose,
though. I mean

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

os.chdir("C:/Example")

is perfectly valid in the Windows API. It is only the command line
processor that requires \ to differentiate from command options.

If that is still too much to enter, I'd recommend one look at REXX... Any statement that is not parsable as a REXX command is normally sent to
the shell (unless one has specified a different command processor), so...

"CD C:\Example"

(with the quotes) is sufficient. (Hmm I may have to check that -- it may
only CD for the one command, then revert to parent directory)


--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

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Dennis Lee Bieber <wlfraed@ix.netcom.com> writes:

If that is still too much to enter, I'd recommend one look at REXX...
Any statement that is not parsable as a REXX command is normally sent to
the shell (unless one has specified a different command processor), so...

I still have vague but fond memories of embedding something
into my texts in the Amiga Cygnus-Ed editor which then would
serve as Cygnus-Ed "macros" activated via hotkeys. I believe
these snippets were written by me in AREXX (REXX for the Amiga,
1987 by William S. Hawes). I forgot all details, though.

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On 21 Dec 2022 17:49:35 GMT, ram@zedat.fu-berlin.de (Stefan Ram) declaimed
the following:

Dennis Lee Bieber <wlfraed@ix.netcom.com> writes:

If that is still too much to enter, I'd recommend one look at REXX... >>Any statement that is not parsable as a REXX command is normally sent to >>the shell (unless one has specified a different command processor), so...

I still have vague but fond memories of embedding something
into my texts in the Amiga Cygnus-Ed editor which then would
serve as Cygnus-Ed "macros" activated via hotkeys. I believe
these snippets were written by me in AREXX (REXX for the Amiga,
1987 by William S. Hawes). I forgot all details, though.

Probably -- AREXX was the most capable version of REXX I've encountered (Regina REXX and ooREXX seem to be limited in the command processors it understands -- basically the equivalent of direct execution ["exec"? style]
or with a shell). It allowed /any/ application that opened an AREXX port to
be command processor. Even the basic text editor could be controlled via
AREXX. Heck, one could even write AREXX scripts that could open ports and become command processors for other scripts.


--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

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