On 5/13/2022 5:38 AM, Lars Ingebrigtsen wrote:
> Jim Porter <jporterbugs@gmail.com> writes:
>> I agree that this would definitely be nice to have though.
> 
> Yup.

And here's a patch series. It's a bit long, so I'll summarize the changes.

The first patch just adds docs/tests for the existing code, plus a bit 
of code cleanup. It also fixes a very small edge case I stumbled upon, 
where "echo foo >a >b >a" only writes to "a". That was just a logic bug 
in 'eshell-set-output-handle'.

The second patch enhances 'eshell-interactive-output-p' so that it can 
check just stdout (or stderr) for interactivity, or all. This is 
technically a behavior change in some functions that call this, but I 
looked through all of them, and I think the new behavior makes more 
sense. This is really just laying the groundwork for the final patch in 
the series though.

The third patch adds all the parsing and command handling for various 
new kinds of redirect operators, like '&>', '2>&1', and '|&'.

The fourth patch moves some internal Eshell process bookkeeping onto the 
process objects. That way, we can reuse this code when making a pipe 
process. I also added some more tests for the existing code (this time 
just for external process handling).

The final patch fixes the actual issue described in this bug. When 
creating an external process, it checks whether stdout and stderr go to 
different places. If so, it makes a pipe process to monitor stderr and 
routes everything as appropriate.