I can't explain the following

I can't explain the following

[Jim]

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Hi everyone,

While working on my .zshenv file I discovered something strange that I
can't explain.
The changes(still a work in progress) had a glob that took some time to
complete
and won't be there when I finish. This made it quite noticeable. Everything
I was
doing in a zsh instance seemed to work normally with one notable exception,
that
I know of.

% less $file      # executes .zshenv before outputting content of file
      If .zshrc has some "test" print statement(s), they are outputs and
not the file??

% < $file       outputs file and pipes it through less ? I should remember
why, anyway!
% cat $file    outputs content of file as expected
% more $file  outputs content of file as expected

What I can't figure out is why zsh/"less" does what it does. Could someone
enlighten me?
Is there a way of "tracing" what is happening?
BTW "less" is not an alias or function.

Distribution:  Devuan
ZSH_VERSION  5.8
ZSH_PATCHLEVEL debian/5.8-6+deb11u1
LESS='-R -M --shift 5'
LESSOPEN='|lesspipe %s'

Thanks in advance for any help you can provide.

Jim Murphy

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Re: I can't explain the following

[Bart Schaefer]

On Tue, Apr 26, 2022 at 8:51 AM Jim <linux.tech.guy@gmail.com> wrote:
>
> What I can't figure out is why zsh/"less" does what it does. Could someone enlighten me?

It's this:

> LESSOPEN='|lesspipe %s'

> Is there a way of "tracing" what is happening?

strace -ff -o tracefile less ...

... and then look through the set of files that are produced.  To save
you the trouble:

execve("/bin/sh", ["sh", "-c", "/bin/zsh -c lesspipe\\ C.gz"],
0x7ffc15c0b800 /* 56 vars */) = 0

Now, why it's running lesspipe with "/bin/zsh -c" instead of with
/bin/sh or at least "/bin/zsh -fc" I don't know.  The doc for "less"
doesn't mention using $SHELL for this case.

Re: I can't explain the following

[Jim]

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If I wasn't testing things in .zshenv, I wouldn't have known anything
about this. Another reason to watch what goes into startup files,
especially .zshenv.

Feels like I'm watching "Catch 22".

On Tue, Apr 26, 2022 at 8:22 PM Bart Schaefer <schaefer@brasslantern.com>
wrote:

> Now, why it's running lesspipe with "/bin/zsh -c" instead of with
> /bin/sh or at least "/bin/zsh -fc" I don't know.  The doc for "less"
> doesn't mention using $SHELL for this case.
>

I wonder if the folks maintaining less would even consider this an issue?
Oh well.
At least I know what is going on, and what I shouldn't do in .zshenv since
I doubt I
will stop using less. Makes me wonder if less is the only command that does
something like this.

Thanks for the info.  Learned my something new for the day.

Jim Murphy

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Re: I can't explain the following

[Bart Schaefer]

On Wed, Apr 27, 2022 at 8:22 AM Jim <linux.tech.guy@gmail.com> wrote:
>
>> Now, why it's running lesspipe with "/bin/zsh -c" instead of with
>> /bin/sh or at least "/bin/zsh -fc" I don't know.
>
> I wonder if the folks maintaining less would even consider this an issue?

That execve() is pretty obviously coming from system().  Try writing a
little C program that calls system() and strace that, maybe the
library is supplying the "/bin/zsh -c" part because lesspipe is a
script (which is also undocumented and potentially wrong, since the
script does have a #! line).

> At least I know what is going on, and what I shouldn't do in .zshenv since I doubt I
> will stop using less.

You could stop setting LESSOPEN.  I long ago decided the "convenience"
of having gzip files etc. automatically unpacked was not worth the
other side-effects.

Re: I can't explain the following

[Jim]

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On Wed, Apr 27, 2022 at 10:59 AM Bart Schaefer <schaefer@brasslantern.com>
wrote:

> You could stop setting LESSOPEN.  I long ago decided the "convenience"
> of having gzip files etc. automatically unpacked was not worth the
> other side-effects.
>

Bye LESSOPEN
If I need to look at "gzip ... etc" files, I can use an alias:

alias lessopen=$'\n(){\n  export LESSOPEN="|lesspipe %s"\n  less $*\n}'

Again, thanks,

Jim

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