Interesting zsh behaviour regarding awk and backslash

Interesting zsh behaviour regarding awk and backslash

[İsmail Dönmez]

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Hi;

gawk 3.1.8

bash:

[~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
\\\\

zsh 4.3.12-dev-1

[~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
\\

Ideas?

P.S: gaw 4.0.0 is buggy with this gsub command and output will differ.

Regards,
ismail

Re: Interesting zsh behaviour regarding awk and backslash

[Jérémie Roquet]

Hi İsmail,

2011/9/27 İsmail Dönmez <ismail@namtrac.org>:
> gawk 3.1.8
>
> bash:
>
> [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> \\\\
>
> zsh 4.3.12-dev-1
>
> [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> \\
>
> Ideas?

Why bother with gawk?

bash$ echo '\\'
\\
zsh$ echo '\\'
\

:p

Best regards,

-- 
Jérémie

Re: Interesting zsh behaviour regarding awk and backslash

[İsmail Dönmez]

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Hi;

On Tue, Sep 27, 2011 at 1:54 PM, Jérémie Roquet <arkanosis@gmail.com> wrote:

> Hi İsmail,
>
> 2011/9/27 İsmail Dönmez <ismail@namtrac.org>:
> > gawk 3.1.8
> >
> > bash:
> >
> > [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> > \\\\
> >
> > zsh 4.3.12-dev-1
> >
> > [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> > \\
> >
> > Ideas?
>
> Why bother with gawk?
>
> bash$ echo '\\'
> \\
> zsh$ echo '\\'
> \
>

Ah cool, I was working on a gawk bug when I noticed this :-)

Regards,
ismail

Re: Interesting zsh behaviour regarding awk and backslash

[Bart Schaefer]

On Sep 27,  1:54pm, Jeremie Roquet wrote:
}
} Why bother with gawk?
} 
} bash$ echo '\\'
} \\
} zsh$ echo '\\'
} \

This isn't quoting behavior, it's "echo" behavior.  If you tell zsh to
act like a standard shell, it does:

% ARGV0=sh zsh -f
$ echo '\\'
\\
$  set -o | grep echo
nobsdecho             off
$ 

Re: Interesting zsh behaviour regarding awk and backslash

[Stephane Chazelas]

2011-09-27 06:48:22 -0700, Bart Schaefer:
> On Sep 27,  1:54pm, Jeremie Roquet wrote:
> }
> } Why bother with gawk?
> } 
> } bash$ echo '\\'
> } \\
> } zsh$ echo '\\'
> } \
> 
> This isn't quoting behavior, it's "echo" behavior.  If you tell zsh to
> act like a standard shell, it does:
> 
> % ARGV0=sh zsh -f
> $ echo '\\'
> \\
> $  set -o | grep echo
> nobsdecho             off
> $ 

standard shells *are meant* to output "\", not "\\". bash is not
standard in that regard. So zsh should *not* change its behavior
when called as sh here.

UNIX (POSIX+XSI) mandates the "\", POSIX makes the behavior of
echo unspecified in that case ("\", "\\" and "ambiguous input"
outputs are all acceptable, echo shouldn't be used in POSIX
scripts where the arguments may contain "\" or start with "-n"
(use printf instead))

zsh is not POSIX (and same for bash) in that it doesn't
output "-e" when called as "echo -e".

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
for the spec.

-- 
Stephane

Re: Interesting zsh behaviour regarding awk and backslash

[Mikael Magnusson]

On 27 September 2011 13:42, İsmail Dönmez <ismail@namtrac.org> wrote:
> Hi;
>
> gawk 3.1.8
>
> bash:
>
> [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> \\\\
>
> zsh 4.3.12-dev-1
>
> [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> \\
>
> Ideas?

setopt bsdecho (it changes whether -e or -E is the default mode).

-- 
Mikael Magnusson

Re: Interesting zsh behaviour regarding awk and backslash

[İsmail Dönmez]

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Hi;

On Tue, Sep 27, 2011 at 3:51 PM, Mikael Magnusson <mikachu@gmail.com> wrote:

> On 27 September 2011 13:42, İsmail Dönmez <ismail@namtrac.org> wrote:
> > Hi;
> >
> > gawk 3.1.8
> >
> > bash:
> >
> > [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> > \\\\
> >
> > zsh 4.3.12-dev-1
> >
> > [~]> echo '\\' | gawk '{gsub("\\\\","\\\\",$0); print($0);}'
> > \\
> >
> > Ideas?
>
> setopt bsdecho (it changes whether -e or -E is the default mode).
>

Thanks that works,  any reason this is not on by default for sh
compatibility though?

Regards.

Re: Interesting zsh behaviour regarding awk and backslash

[Frank Terbeck]

İsmail Dönmez wrote:
> On Tue, Sep 27, 2011 at 3:51 PM, Mikael Magnusson <mikachu@gmail.com> wrote:
>> On 27 September 2011 13:42, İsmail Dönmez <ismail@namtrac.org> wrote:
[...]
>> > Ideas?
>>
>> setopt bsdecho (it changes whether -e or -E is the default mode).
>>
>
> Thanks that works,  any reason this is not on by default for sh
> compatibility though?

You can't really portable with `echo'. Even the POSIX section about
`echo' explicitly says something like "For portable applications, use
`printf' instead.".

Regards, Frank

-- 
In protocol design, perfection has been reached not when there is
nothing left to add, but when there is nothing left to take away.
                                                  -- RFC 1925

Re: Interesting zsh behaviour regarding awk and backslash

[Bart Schaefer]

On Sep 27,  3:54pm, Ismail Donmez wrote:
}
} Thanks that works,  any reason this is not on by default for sh
} compatibility though?

Because zsh is quite deliberately not sh compatible by default?

Re: Interesting zsh behaviour regarding awk and backslash

[İsmail Dönmez]

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Hi;

On Tue, Sep 27, 2011 at 4:20 PM, Bart Schaefer <schaefer@brasslantern.com>wrote:

> On Sep 27,  3:54pm, Ismail Donmez wrote:
> }
> } Thanks that works,  any reason this is not on by default for sh
> } compatibility though?
>
> Because zsh is quite deliberately not sh compatible by default?
>

Well ok, this was from a script which explicitly stated /bin/sh so this is a
non-issue for me, just wondered.

Regards,
ismail