Fish shell input redirection from subshell output

Question

When I want to run Wireshark locally to display a packet capture running on another machine, this works on bash, using input redirection from the output of a subshell:

wireshark -k -i <(ssh user@machine "sudo dumpcap -P -w - -f '<filter>' -i eth0")

From what I could find, the syntax for similar behavior on the fish shell is the same but when I run that command on fish, I get the Wireshark output on the terminal but can't see the Wireshark window.

Is there something I'm missing?

Selie

Answer 1

The fish equivalent of <() isn't well suited to this use case. Is there some reason you can't use this simpler and more portable formulation?

ssh user@machine "sudo dumpcap -P -w - -f '<filter>' -i eth0" | wireshark -k -i -

Enyedy

@Olivo 's answer didn't work for me, the behavior was still the same (Wireshark window did not display locally), maybe there's something else missing... This did it though, thanks. – Selie

Answer 2

What you're using there in bash is process substitution (the <() syntax). It is a bash specific syntax (although zsh adopted this same syntax along with its own =()).

fish does have process substitution under a different syntax ((process | psub)). For example:

wireshark -k -i (ssh user@machine "sudo dumpcap -P -w - -f '<filter>' -i eth0" | psub)

---

bash        | equivalent in fish
----------- | ------------------
cat <(ls)   | cat (ls|psub)
ls > >(cat) | N/A (need to find a way to use a pipe, e.g. ls|cat)

Olivo

According to the documentation, there's no fish equivalent to >(ls) – Cheddar

@glennjackman - Correct, thanks, and i was confident that i tested it. (psub|cat) does not fail, but it gives the temporary FIFO name not a stream. – Olivo