Permit combining stdout/stderr as streams to external command behind pipe

[x10an14]

Question

Given command foo, which outputs both stdout and stderr, how can I pipe both of stdout and stderr from foo into bar through a pipe?

Ref these (non-exhaustive list of) alternatives which achieve this in bash:

foo |& bar
foo 2>&1 | bar

Additional context and details

The only way for me to automate checking of my flake.nix checks (in a nice graphical output) in Nushell when using nom now is this arcane invocation:

bash -c 'nix flake check --log-format internal-json -vv |& nom --json'

Feels weird that I cannot do the equivalent of "combine outputs and redirect them through pipe" in Nushell =S

[fdncred]

You could try the complete command but it won't interleave stderr and stdout.

❯ do { ^ls } | complete
╭───────────┬─────────────────────╮
│ stdout    │ CODE_OF_CONDUCT.md  │
│           │ CONTRIBUTING.md     │
│           │ Cargo.lock          │
│           │ Cargo.toml          │
│           │ Cross.toml          │
│ stderr    │                     │
│ exit_code │ 0                   │
╰───────────┴─────────────────────╯

[hardfau1t]

You could try the complete command but it won't interleave stderr and stdout.

• it won't work for stream data, data will be availabe once the program exits

[x10an14]

You could try the complete command but it won't interleave stderr and stdout.

• it won't work for stream data, data will be availabe once the program exits

Thank you for the clarification! The intent behind the example given is to receive streamed data to get a nice visualization of the progress =)

[x10an14]

Considering the replies received so far, should this become a feature request instead?

[hardfau1t]

Considering the replies received so far, should this become a feature request instead?

IMO it should be, AFAIK there is no straight way to do this(not sure whether it is possible or not) and it is most common in unix systems

[amtoine]

@x10an14
you can just update the title and the body of this issue to make it a feature request 😉

[x10an14]

@amtoine: @x10an14 you can just update the title and the body of this issue to make it a feature request 😉

Will you replace the question label/add the feature flag label? =)

[fdncred]

done

[amtoine]

thanks @x10an14 😊

[Spickelbing]

I had the same problem just now and went with run-external --redirect-combine foo | bar. But a shorter way to do this would help.

[x10an14]

I had the same problem just now and went with run-external --redirect-combine foo | bar. But a shorter way to do this would help.

Can you link/reference/document the redirect-combine flag? And never heard of it or it's command. I have yet to check if it's a built-in

[fdncred]

https://www.nushell.sh/commands/docs/run-external.html

I think this is the PR where it was added in April.
#8918

[x10an14]

The run-external --redirect-combine tip works! But only if I quote each and every word starting with a hyphen (read: flag) like so (it seems):

run-external --redirect-combine nix flake check "--log-format" internal-json "-v" | nom --json

While this is of course much better than my previous "use bash" solution, would run-external (by its intent and nature) not be better suited to pass all inputs starting with - to the command its encompassing/running?

Dunno how, but force ordering of flags for run-external to come before the wrapped command maybe?

[x10an14]

This is how it looks like if I don't quoute all flags sent to wrapped binary/command:

2023-08-16 17:18:03+02:00: ~/Doc/sr./nix-configs via ❄️  impure (nix-shell-env)
x10an14@nav-840G8-laptop ❯ > run-external --redirect-combine nix flake check "--log-format" internal-json -v | nom --json
Error: nu::parser::unknown_flag

  × The `run-external` command doesn't have flag `-v`.
   ╭─[entry #3:1:1]
 1 │ run-external --redirect-combine nix flake check "--log-format" internal-json -v | nom --json
   ·                                                                               ┬
   ·                                                                               ╰── unknown flag
   ╰────
  help: Available flags: --help(-h), --redirect-stdout, --redirect-stderr, --redirect-combine, --trim-end-newline.
        Use `--help` for more information.

[CAD97]

A helper to prevent run-external from trying to interpret your command's flags:

def --wrapped run [cmd ...args] { run-external --redirect-combine $cmd $args }

For the convenience you give up the ability to control the flags given to run-external, but get an experience much closer to how ^ works. Each flag you define on run can't be passed through without quoting, but using the wrapper limits that to exclusively just the automatic --help(-h) switch.

A more principled solution would be to teach Nu how to use -- to delineate the end of flags and that all following args are rest arguments. The best solution would probably be to be able to combine "retroactively" and do something like ^external | combine like you can do ^external | complete.