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Comment by mattpallissard | Hacker News Reader

I'm a zsh user, but one thing I miss from bash is /dev/tcp redirection.

    ~  echo <>/dev/tcp/google.com/80
    ~  echo $?
    0
    ~  echo <>/dev/tcp/localhost/80
    bash: connect: Network is unreachable
    bash: /dev/tcp/localhost/80: Network is unreachable
    ~  echo $?
    1

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What about https://zsh.sourceforge.io/Doc/Release/TCP-Function-System.h...?

I think that’s Linux-only, right?

It's in the /dev/ folder so it looks like a device file provided by the operating system.

But it's not. It's a bash built in pseudo file. So it should work in bash on other operating systems.

Nice thing to learn - thanks. Although the only scenario I can think of at the moment would be the lack of netcat (and telnet).

Not a fan of limiting scripts with bashisms. I like them to be runnable under zsh and similar shells despite having /usr/bin/env bash, /bin/bash, /bin/sh shebang.

A more sneaky use case is for reverse shell payload when you have code execution :)

You're right, it does work on macOS.

What other cool use cases could it achieve besides checking if a domain is reachable?

Thanks. I've not seen that before, that's cool.

Why? There’s nc.

I tend to prefer telnet to test connections because its output is more verbose.

We need a friendlier netcat, with better output. Call it netdog.

nc generally provides more verbosity with -v and other options.

nc -v itself is pretty much telnet as far as TCP connections go (TELNET is itself another protocol on top of TCP).

In fact on macOS, I alias telnet=’nc -v’.

Anyway my intent wasn’t to directly challenge your method, this is just a more shell-independent and universal method of doing the same.

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