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Re: bash vs. dash and stdin

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On 22/11/2023 19:17, Greg Wooledge wrote:
> On Wed, Nov 22, 2023 at 07:06:58PM +0700, Max Nikulin wrote:
>>
>>     ssh localhost echo remote
>>     echo local
> 
> This is like <https://mywiki.wooledge.org/BashFAQ/089>.  ssh grabs
> all of the stdin (until EOF) and leaves none for bash.

Thanks. I expected to find it among pitfalls.

> I don't know dash's internals.  Maybe dash reads an entire buffer's
> worth of stdin at a time, instead of a command at a time as bash does.

It seems dash reads a block from stdin (and does not lseek back even for 
regular files) only for commands. I do not see significant difference 
when commands reading stdin are placed into a script

cmd='seq 1000000 | while read -r var ; do
   printf "%s\n" "$var" ;
   ssh localhost echo remote ;
done'
bash -c "$cmd"
dash -c "$cmd"

>> If the script is passed as an argument, not to stdin, then output contains
>> "local" in both cases.
> 
> Yes.  In that case, bash is not competing with ssh for stdin.

I have found an attempt to report it:

https://lore.kernel.org/dash/6640a8ee-eda0-1e35-df1a-c8b303440ca1@mail.de/
stdin should be consumed line by line. Fri, 22 Oct 2021 13:11:43 +0200

No response.

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bash vs. dash and stdin Max Nikulin <manikulin@gmail.com> - 2023-11-22 13:10 +0100
  Re: bash vs. dash and stdin Greg Wooledge <greg@wooledge.org> - 2023-11-22 13:20 +0100
    Re: bash vs. dash and stdin Max Nikulin <manikulin@gmail.com> - 2023-11-23 12:10 +0100
  Re: bash vs. dash and stdin Nicolas George <george@nsup.org> - 2023-11-22 13:20 +0100

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