Re: /dev/tcp

On 8/20/26 09:50, Rich wrote:
> Eli the Bearded <*@eli.users.panix.com> wrote:
>> What system(s) have /dev/tcp/* natively?
> 
> What "systems"?  Only those with a /bin/bash compiled with this
> "special bash feature" compiled in.
> 
>>    $ man bash
>>    [...]
>>    REDIRECTION
>>    [...]
>>         Bash handles several filenames specially when they are used in
>>         redirections,  as described  in the  following table.   If the
>>         operating  system on  which  bash is  running  provides  these
>>         special files, bash will use them;  other wise it will emulate
>>         them internally with the behavior described below.
>>    [...]
>>                /dev/tcp/host/port
>>                    If  host  is a valid  hostname or Internet address,
>>                    and port is an integer port number or service name,
>>                    bash attempts to open the corresponding TCP socket.
>>
>> I don't see it on the various systems I have handy (Debian 13, Amazon
>> Linux 2023, Mac OS 15.7.x, NetBSD 10.1, Android 14).
> 
>> is it a plan9 thing?
> 
> It's a Bash feature.  Note the man page quote you provided:
> 
>>   **Bash** handles several filenames specially when they are used in
>>   redirections
> 
> These are handled by Bash, they don't exist as part of the OS (system).

   Correct. I've used the /dev/tcp trick before to
   check ports. Seems to only work with Bash. Others
   might add it eventually, but not too likely.

   Other odd Linux tricks - how many know you can
   read/write to a disk drive that has no file
   system ? GParted does have an option that creates
   a "blank" drive. It's an old trick, squeeze in
   more raw data. To a degree, it can make that data
   a bit more "portable" because it's not tied to
   EXT?/NTFS/XFS/etc. You just need a system that
   can open the 'blank' as an I/O device.